diff --git a/examples/index-pack.c b/examples/index-pack.c
index 0f8234c7591..e9f32b8b291 100644
--- a/examples/index-pack.c
+++ b/examples/index-pack.c
@@ -29,7 +29,7 @@ int lg2_index_pack(git_repository *repo, int argc, char **argv)
 	}
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	error = git_indexer_new(&idx, ".", git_repository_oid_type(repo), NULL);
+	error = git_indexer_new(&idx, ".", NULL);
 #else
 	error = git_indexer_new(&idx, ".", 0, NULL, NULL);
 #endif
diff --git a/examples/show-index.c b/examples/show-index.c
index 0a5e7d1a2e4..ac0040874ec 100644
--- a/examples/show-index.c
+++ b/examples/show-index.c
@@ -31,7 +31,7 @@ int lg2_show_index(git_repository *repo, int argc, char **argv)
 	dirlen = strlen(dir);
 	if (dirlen > 5 && strcmp(dir + dirlen - 5, "index") == 0) {
 #ifdef GIT_EXPERIMENTAL_SHA256
-		check_lg2(git_index_open(&index, dir, GIT_OID_SHA1), "could not open index", dir);
+		check_lg2(git_index_open(&index, dir, NULL), "could not open index", dir);
 #else
 		check_lg2(git_index_open(&index, dir), "could not open index", dir);
 #endif
diff --git a/fuzzers/packfile_fuzzer.c b/fuzzers/packfile_fuzzer.c
index aeba9575c3e..bcbdd8bc40b 100644
--- a/fuzzers/packfile_fuzzer.c
+++ b/fuzzers/packfile_fuzzer.c
@@ -84,7 +84,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 	}
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	error = git_indexer_new(&indexer, ".", GIT_OID_SHA1, NULL);
+	error = git_indexer_new(&indexer, ".", NULL);
 #else
 	error = git_indexer_new(&indexer, ".", 0, odb, NULL);
 #endif
diff --git a/include/git2/index.h b/include/git2/index.h
index 9f3efe1fc7e..0adff1abd95 100644
--- a/include/git2/index.h
+++ b/include/git2/index.h
@@ -191,25 +191,69 @@ typedef enum {
 
 #ifdef GIT_EXPERIMENTAL_SHA256
 
+/**
+ * The options for opening or creating an index.
+ *
+ * Initialize with `GIT_INDEX_OPTIONS_INIT`. Alternatively, you can
+ * use `git_index_options_init`.
+ *
+ * @options[version] GIT_INDEX_OPTIONS_VERSION
+ * @options[init_macro] GIT_INDEX_OPTIONS_INIT
+ * @options[init_function] git_index_options_init
+ */
+typedef struct git_index_options {
+	unsigned int version; /**< The version */
+
+	/**
+	 * The object ID type for the object IDs that exist in the index.
+	 *
+	 * If this is not specified, this defaults to `GIT_OID_SHA1`.
+	 */
+	git_oid_t oid_type;
+} git_index_options;
+
+/** Current version for the `git_index_options` structure */
+#define GIT_INDEX_OPTIONS_VERSION 1
+
+/** Static constructor for `git_index_options` */
+#define GIT_INDEX_OPTIONS_INIT { GIT_INDEX_OPTIONS_VERSION }
+
+/**
+ * Initialize git_index_options structure
+ *
+ * Initializes a `git_index_options` with default values. Equivalent to creating
+ * an instance with GIT_INDEX_OPTIONS_INIT.
+ *
+ * @param opts The `git_index_options` struct to initialize.
+ * @param version The struct version; pass `GIT_INDEX_OPTIONS_VERSION`.
+ * @return Zero on success; -1 on failure.
+ */
+GIT_EXTERN(int) git_index_options_init(
+	git_index_options *opts,
+	unsigned int version);
+
 /**
  * Creates a new bare Git index object, without a repository to back
  * it. This index object is capable of storing SHA256 objects.
  *
  * @param index_out the pointer for the new index
  * @param index_path the path to the index file in disk
- * @param oid_type the object ID type to use for the repository
+ * @param opts the options for opening the index, or NULL
  * @return 0 or an error code
  */
-GIT_EXTERN(int) git_index_open(git_index **index_out, const char *index_path, git_oid_t oid_type);
+GIT_EXTERN(int) git_index_open(
+	git_index **index_out,
+	const char *index_path,
+	const git_index_options *opts);
 
 /**
  * Create an in-memory index object.
  *
  * @param index_out the pointer for the new index
- * @param oid_type the object ID type to use for the repository
+ * @param opts the options for opening the index, or NULL
  * @return 0 or an error code
  */
-GIT_EXTERN(int) git_index_new(git_index **index_out, git_oid_t oid_type);
+GIT_EXTERN(int) git_index_new(git_index **index_out, const git_index_options *opts);
 
 #else
 
diff --git a/include/git2/indexer.h b/include/git2/indexer.h
index d47ce2c1885..9aaedc3c43f 100644
--- a/include/git2/indexer.h
+++ b/include/git2/indexer.h
@@ -77,6 +77,9 @@ typedef struct git_indexer_options {
 	/** permissions to use creating packfile or 0 for defaults */
 	unsigned int mode;
 
+	/** the type of object ids in the packfile or 0 for SHA1 */
+	git_oid_t oid_type;
+
 	/**
 	 * object database from which to read base objects when
 	 * fixing thin packs. This can be NULL if there are no thin
@@ -120,13 +123,12 @@ GIT_EXTERN(int) git_indexer_options_init(
  *
  * @param out where to store the indexer instance
  * @param path to the directory where the packfile should be stored
- * @param oid_type the oid type to use for objects
+ * @param opts the options to create the indexer with
  * @return 0 or an error code.
  */
 GIT_EXTERN(int) git_indexer_new(
 		git_indexer **out,
 		const char *path,
-		git_oid_t oid_type,
 		git_indexer_options *opts);
 #else
 /**
diff --git a/include/git2/repository.h b/include/git2/repository.h
index 59c4d0f30d6..b203576affc 100644
--- a/include/git2/repository.h
+++ b/include/git2/repository.h
@@ -10,6 +10,7 @@
 #include "common.h"
 #include "types.h"
 #include "oid.h"
+#include "odb.h"
 #include "buffer.h"
 #include "commit.h"
 
@@ -52,15 +53,6 @@ GIT_EXTERN(int) git_repository_open(git_repository **out, const char *path);
  */
 GIT_EXTERN(int) git_repository_open_from_worktree(git_repository **out, git_worktree *wt);
 
-#ifdef GIT_EXPERIMENTAL_SHA256
-
-GIT_EXTERN(int) git_repository_wrap_odb(
-	git_repository **out,
-	git_odb *odb,
-	git_oid_t oid_type);
-
-#else
-
 /**
  * Create a "fake" repository to wrap an object database
  *
@@ -76,8 +68,6 @@ GIT_EXTERN(int) git_repository_wrap_odb(
 	git_repository **out,
 	git_odb *odb);
 
-#endif
-
 /**
  * Look for a git repository and copy its path in the given buffer.
  * The lookup start from base_path and walk across parent directories
diff --git a/include/git2/sys/commit_graph.h b/include/git2/sys/commit_graph.h
index 838efee55bf..ff547ef0c1f 100644
--- a/include/git2/sys/commit_graph.h
+++ b/include/git2/sys/commit_graph.h
@@ -19,6 +19,45 @@
  */
 GIT_BEGIN_DECL
 
+/**
+ * Options structure for `git_commit_graph_open_new`.
+ *
+ * Initialize with `GIT_COMMIT_GRAPH_OPEN_OPTIONS_INIT`. Alternatively,
+ * you can use `git_commit_graph_open_options_init`.
+ */
+typedef struct {
+	unsigned int version;
+
+#ifdef GIT_EXPERIMENTAL_SHA256
+	/** The object ID type that this commit graph contains. */
+	git_oid_t oid_type;
+#endif
+} git_commit_graph_open_options;
+
+/** Current version for the `git_commit_graph_open_options` structure */
+#define GIT_COMMIT_GRAPH_OPEN_OPTIONS_VERSION 1
+
+/** Static constructor for `git_commit_graph_open_options` */
+#define GIT_COMMIT_GRAPH_OPEN_OPTIONS_INIT { \
+		GIT_COMMIT_GRAPH_OPEN_OPTIONS_VERSION \
+	}
+
+/**
+ * Initialize git_commit_graph_open_options structure
+ *
+ * Initializes a `git_commit_graph_open_options` with default values.
+ * Equivalent to creating an instance with
+ * `GIT_COMMIT_GRAPH_OPEN_OPTIONS_INIT`.
+ *
+ * @param opts The `git_commit_graph_open_options` struct to initialize.
+ * @param version The struct version; pass `GIT_COMMIT_GRAPH_OPEN_OPTIONS_VERSION`.
+ * @return Zero on success; -1 on failure.
+ */
+GIT_EXTERN(int) git_commit_graph_open_options_init(
+	git_commit_graph_open_options *opts,
+	unsigned int version);
+
+
 /**
  * Opens a `git_commit_graph` from a path to an objects directory.
  *
@@ -32,7 +71,7 @@ GIT_EXTERN(int) git_commit_graph_open(
 	git_commit_graph **cgraph_out,
 	const char *objects_dir
 #ifdef GIT_EXPERIMENTAL_SHA256
-	, git_oid_t oid_type
+	, const git_commit_graph_open_options *options
 #endif
 	);
 
@@ -46,54 +85,6 @@ GIT_EXTERN(int) git_commit_graph_open(
  */
 GIT_EXTERN(void) git_commit_graph_free(git_commit_graph *cgraph);
 
-/**
- * Create a new writer for `commit-graph` files.
- *
- * @param out Location to store the writer pointer.
- * @param objects_info_dir The `objects/info` directory.
- * The `commit-graph` file will be written in this directory.
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_commit_graph_writer_new(
-		git_commit_graph_writer **out,
-		const char *objects_info_dir
-#ifdef GIT_EXPERIMENTAL_SHA256
-	, git_oid_t oid_type
-#endif
-		);
-
-/**
- * Free the commit-graph writer and its resources.
- *
- * @param w The writer to free. If NULL no action is taken.
- */
-GIT_EXTERN(void) git_commit_graph_writer_free(git_commit_graph_writer *w);
-
-/**
- * Add an `.idx` file (associated to a packfile) to the writer.
- *
- * @param w The writer.
- * @param repo The repository that owns the `.idx` file.
- * @param idx_path The path of an `.idx` file.
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_commit_graph_writer_add_index_file(
-		git_commit_graph_writer *w,
-		git_repository *repo,
-		const char *idx_path);
-
-/**
- * Add a revwalk to the writer. This will add all the commits from the revwalk
- * to the commit-graph.
- *
- * @param w The writer.
- * @param walk The git_revwalk.
- * @return 0 or an error code
- */
-GIT_EXTERN(int) git_commit_graph_writer_add_revwalk(
-		git_commit_graph_writer *w,
-		git_revwalk *walk);
-
 
 /**
  * The strategy to use when adding a new set of commits to a pre-existing
@@ -108,15 +99,19 @@ typedef enum {
 } git_commit_graph_split_strategy_t;
 
 /**
- * Options structure for
- * `git_commit_graph_writer_commit`/`git_commit_graph_writer_dump`.
+ * Options structure for `git_commit_graph_writer_new`.
  *
- * Initialize with `GIT_COMMIT_GRAPH_WRITER_OPTIONS_INIT`. Alternatively, you
- * can use `git_commit_graph_writer_options_init`.
+ * Initialize with `GIT_COMMIT_GRAPH_WRITER_OPTIONS_INIT`. Alternatively,
+ * you can use `git_commit_graph_writer_options_init`.
  */
 typedef struct {
 	unsigned int version;
 
+#ifdef GIT_EXPERIMENTAL_SHA256
+	/** The object ID type that this commit graph contains. */
+	git_oid_t oid_type;
+#endif
+
 	/**
 	 * The strategy to use when adding new commits to a pre-existing commit-graph
 	 * chain.
@@ -158,29 +153,71 @@ GIT_EXTERN(int) git_commit_graph_writer_options_init(
 	git_commit_graph_writer_options *opts,
 	unsigned int version);
 
+/**
+ * Create a new writer for `commit-graph` files.
+ *
+ * @param out Location to store the writer pointer.
+ * @param objects_info_dir The `objects/info` directory.
+ * The `commit-graph` file will be written in this directory.
+ * @param options The options for the commit graph writer.
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_commit_graph_writer_new(
+		git_commit_graph_writer **out,
+		const char *objects_info_dir,
+		const git_commit_graph_writer_options *options);
+
+/**
+ * Free the commit-graph writer and its resources.
+ *
+ * @param w The writer to free. If NULL no action is taken.
+ */
+GIT_EXTERN(void) git_commit_graph_writer_free(git_commit_graph_writer *w);
+
+/**
+ * Add an `.idx` file (associated to a packfile) to the writer.
+ *
+ * @param w The writer.
+ * @param repo The repository that owns the `.idx` file.
+ * @param idx_path The path of an `.idx` file.
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_commit_graph_writer_add_index_file(
+		git_commit_graph_writer *w,
+		git_repository *repo,
+		const char *idx_path);
+
+/**
+ * Add a revwalk to the writer. This will add all the commits from the revwalk
+ * to the commit-graph.
+ *
+ * @param w The writer.
+ * @param walk The git_revwalk.
+ * @return 0 or an error code
+ */
+GIT_EXTERN(int) git_commit_graph_writer_add_revwalk(
+		git_commit_graph_writer *w,
+		git_revwalk *walk);
+
 /**
  * Write a `commit-graph` file to a file.
  *
  * @param w The writer
- * @param opts Pointer to git_commit_graph_writer_options struct.
  * @return 0 or an error code
  */
 GIT_EXTERN(int) git_commit_graph_writer_commit(
-		git_commit_graph_writer *w,
-		git_commit_graph_writer_options *opts);
+		git_commit_graph_writer *w);
 
 /**
  * Dump the contents of the `commit-graph` to an in-memory buffer.
  *
- * @param buffer Buffer where to store the contents of the `commit-graph`.
+ * @param[out] buffer Buffer where to store the contents of the `commit-graph`.
  * @param w The writer.
- * @param opts Pointer to git_commit_graph_writer_options struct.
  * @return 0 or an error code
  */
 GIT_EXTERN(int) git_commit_graph_writer_dump(
 		git_buf *buffer,
-		git_commit_graph_writer *w,
-		git_commit_graph_writer_options *opts);
+		git_commit_graph_writer *w);
 
 /** @} */
 GIT_END_DECL
diff --git a/include/git2/sys/midx.h b/include/git2/sys/midx.h
index 2bf0d01eb48..b3a68afbfc5 100644
--- a/include/git2/sys/midx.h
+++ b/include/git2/sys/midx.h
@@ -19,6 +19,44 @@
  */
 GIT_BEGIN_DECL
 
+/**
+ * Options structure for `git_midx_writer_options`.
+ *
+ * Initialize with `GIT_MIDX_WRITER_OPTIONS_INIT`. Alternatively,
+ * you can use `git_midx_writer_options_init`.
+ */
+typedef struct {
+	unsigned int version;
+
+#ifdef GIT_EXPERIMENTAL_SHA256
+	/** The object ID type that this commit graph contains. */
+	git_oid_t oid_type;
+#endif
+} git_midx_writer_options;
+
+/** Current version for the `git_midx_writer_options` structure */
+#define GIT_MIDX_WRITER_OPTIONS_VERSION 1
+
+/** Static constructor for `git_midx_writer_options` */
+#define GIT_MIDX_WRITER_OPTIONS_INIT { \
+		GIT_MIDX_WRITER_OPTIONS_VERSION \
+	}
+
+/**
+ * Initialize git_midx_writer_options structure
+ *
+ * Initializes a `git_midx_writer_options` with default values.
+ * Equivalent to creating an instance with
+ * `GIT_MIDX_WRITER_OPTIONS_INIT`.
+ *
+ * @param opts The `git_midx_writer_options` struct to initialize.
+ * @param version The struct version; pass `GIT_MIDX_WRITER_OPTIONS_VERSION`.
+ * @return Zero on success; -1 on failure.
+ */
+GIT_EXTERN(int) git_midx_writer_options_init(
+	git_midx_writer_options *opts,
+	unsigned int version);
+
 /**
  * Create a new writer for `multi-pack-index` files.
  *
@@ -31,7 +69,7 @@ GIT_EXTERN(int) git_midx_writer_new(
 		git_midx_writer **out,
 		const char *pack_dir
 #ifdef GIT_EXPERIMENTAL_SHA256
-		, git_oid_t oid_type
+		, git_midx_writer_options *options
 #endif
 		);
 
diff --git a/include/git2/sys/repository.h b/include/git2/sys/repository.h
index eb0a33a92de..026ac8a1d1a 100644
--- a/include/git2/sys/repository.h
+++ b/include/git2/sys/repository.h
@@ -22,14 +22,56 @@ GIT_BEGIN_DECL
 
 #ifdef GIT_EXPERIMENTAL_SHA256
 
+/**
+ * The options for creating an repository from scratch.
+ *
+ * Initialize with `GIT_REPOSITORY_NEW_OPTIONS_INIT`. Alternatively,
+ * you can use `git_repository_new_options_init`.
+ *
+ * @options[version] GIT_REPOSITORY_NEW_OPTIONS_VERSION
+ * @options[init_macro] GIT_REPOSITORY_NEW_OPTIONS_INIT
+ * @options[init_function] git_repository_new_options_init
+ */
+typedef struct git_repository_new_options {
+	unsigned int version; /**< The version */
+
+	/**
+	 * The object ID type for the object IDs that exist in the index.
+	 *
+	 * If this is not specified, this defaults to `GIT_OID_SHA1`.
+	 */
+	git_oid_t oid_type;
+} git_repository_new_options;
+
+/** Current version for the `git_repository_new_options` structure */
+#define GIT_REPOSITORY_NEW_OPTIONS_VERSION 1
+
+/** Static constructor for `git_repository_new_options` */
+#define GIT_REPOSITORY_NEW_OPTIONS_INIT { GIT_REPOSITORY_NEW_OPTIONS_VERSION }
+
+/**
+ * Initialize git_repository_new_options structure
+ *
+ * Initializes a `git_repository_new_options` with default values.
+ * Equivalent to creating an instance with
+ * `GIT_REPOSITORY_NEW_OPTIONS_INIT`.
+ *
+ * @param opts The `git_repository_new_options` struct to initialize.
+ * @param version The struct version; pass `GIT_REPOSITORY_NEW_OPTIONS_VERSION`.
+ * @return Zero on success; -1 on failure.
+ */
+GIT_EXTERN(int) git_repository_new_options_init(
+	git_repository_new_options *opts,
+	unsigned int version);
+
 /**
  * Create a new repository with no backends.
  *
  * @param[out] out The blank repository
- * @param oid_type the object ID type for this repository
+ * @param opts the options for repository creation, or NULL for defaults
  * @return 0 on success, or an error code
  */
-GIT_EXTERN(int) git_repository_new(git_repository **out, git_oid_t oid_type);
+GIT_EXTERN(int) git_repository_new(git_repository **out, git_repository_new_options *opts);
 #else
 
 /**
diff --git a/src/cli/cmd_index_pack.c b/src/cli/cmd_index_pack.c
index b8e9749de6a..6a67990b47d 100644
--- a/src/cli/cmd_index_pack.c
+++ b/src/cli/cmd_index_pack.c
@@ -78,7 +78,9 @@ int cmd_index_pack(int argc, char **argv)
 	}
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	ret = git_indexer_new(&idx, ".", GIT_OID_SHA1, &idx_opts);
+	idx_opts.oid_type = GIT_OID_SHA1;
+
+	ret = git_indexer_new(&idx, ".", &idx_opts);
 #else
 	ret = git_indexer_new(&idx, ".", 0, NULL, &idx_opts);
 #endif
diff --git a/src/libgit2/commit_graph.c b/src/libgit2/commit_graph.c
index 8fd59692730..92785049e4e 100644
--- a/src/libgit2/commit_graph.c
+++ b/src/libgit2/commit_graph.c
@@ -365,15 +365,24 @@ int git_commit_graph_open(
 	git_commit_graph **cgraph_out,
 	const char *objects_dir
 #ifdef GIT_EXPERIMENTAL_SHA256
-	, git_oid_t oid_type
+	, const git_commit_graph_open_options *opts
 #endif
 	)
 {
-#ifndef GIT_EXPERIMENTAL_SHA256
-	git_oid_t oid_type = GIT_OID_SHA1;
-#endif
+	git_oid_t oid_type;
 	int error;
 
+#ifdef GIT_EXPERIMENTAL_SHA256
+	GIT_ERROR_CHECK_VERSION(opts,
+		GIT_COMMIT_GRAPH_OPEN_OPTIONS_VERSION,
+		"git_commit_graph_open_options");
+
+	oid_type = opts && opts->oid_type ? opts->oid_type : GIT_OID_DEFAULT;
+	GIT_ASSERT_ARG(git_oid_type_is_valid(oid_type));
+#else
+	oid_type = GIT_OID_SHA1;
+#endif
+
 	error = git_commit_graph_new(cgraph_out, objects_dir, true,
 			oid_type);
 
@@ -684,21 +693,40 @@ static int packed_commit__cmp(const void *a_, const void *b_)
 	return git_oid_cmp(&a->sha1, &b->sha1);
 }
 
+int git_commit_graph_writer_options_init(
+	git_commit_graph_writer_options *opts,
+	unsigned int version)
+{
+	GIT_INIT_STRUCTURE_FROM_TEMPLATE(
+		opts,
+		version,
+		git_commit_graph_writer_options,
+		GIT_COMMIT_GRAPH_WRITER_OPTIONS_INIT);
+	return 0;
+}
+
 int git_commit_graph_writer_new(
 	git_commit_graph_writer **out,
-	const char *objects_info_dir
-#ifdef GIT_EXPERIMENTAL_SHA256
-	, git_oid_t oid_type
-#endif
+	const char *objects_info_dir,
+	const git_commit_graph_writer_options *opts
 	)
 {
 	git_commit_graph_writer *w;
+	git_oid_t oid_type;
+
+#ifdef GIT_EXPERIMENTAL_SHA256
+	GIT_ERROR_CHECK_VERSION(opts,
+		GIT_COMMIT_GRAPH_WRITER_OPTIONS_VERSION,
+		"git_commit_graph_writer_options");
 
-#ifndef GIT_EXPERIMENTAL_SHA256
-	git_oid_t oid_type = GIT_OID_SHA1;
+	oid_type = opts && opts->oid_type ? opts->oid_type : GIT_OID_DEFAULT;
+	GIT_ASSERT_ARG(git_oid_type_is_valid(oid_type));
+#else
+	GIT_UNUSED(opts);
+	oid_type = GIT_OID_SHA1;
 #endif
 
-	GIT_ASSERT_ARG(out && objects_info_dir && oid_type);
+	GIT_ASSERT_ARG(out && objects_info_dir);
 
 	w = git__calloc(1, sizeof(git_commit_graph_writer));
 	GIT_ERROR_CHECK_ALLOC(w);
@@ -775,9 +803,9 @@ static int object_entry__cb(const git_oid *id, void *data)
 }
 
 int git_commit_graph_writer_add_index_file(
-		git_commit_graph_writer *w,
-		git_repository *repo,
-		const char *idx_path)
+	git_commit_graph_writer *w,
+	git_repository *repo,
+	const char *idx_path)
 {
 	int error;
 	struct git_pack_file *p = NULL;
@@ -1043,9 +1071,9 @@ static void packed_commit_free_dup(void *packed_commit)
 }
 
 static int commit_graph_write(
-		git_commit_graph_writer *w,
-		commit_graph_write_cb write_cb,
-		void *cb_data)
+	git_commit_graph_writer *w,
+	commit_graph_write_cb write_cb,
+	void *cb_data)
 {
 	int error = 0;
 	size_t i;
@@ -1249,30 +1277,13 @@ static int commit_graph_write_filebuf(const char *buf, size_t size, void *data)
 	return git_filebuf_write(f, buf, size);
 }
 
-int git_commit_graph_writer_options_init(
-	git_commit_graph_writer_options *opts,
-	unsigned int version)
-{
-	GIT_INIT_STRUCTURE_FROM_TEMPLATE(
-			opts,
-			version,
-			git_commit_graph_writer_options,
-			GIT_COMMIT_GRAPH_WRITER_OPTIONS_INIT);
-	return 0;
-}
-
-int git_commit_graph_writer_commit(
-		git_commit_graph_writer *w,
-		git_commit_graph_writer_options *opts)
+int git_commit_graph_writer_commit(git_commit_graph_writer *w)
 {
 	int error;
 	int filebuf_flags = GIT_FILEBUF_DO_NOT_BUFFER;
 	git_str commit_graph_path = GIT_STR_INIT;
 	git_filebuf output = GIT_FILEBUF_INIT;
 
-	/* TODO: support options and fill in defaults. */
-	GIT_UNUSED(opts);
-
 	error = git_str_joinpath(
 			&commit_graph_path, git_str_cstr(&w->objects_info_dir), "commit-graph");
 	if (error < 0)
@@ -1296,18 +1307,14 @@ int git_commit_graph_writer_commit(
 
 int git_commit_graph_writer_dump(
 	git_buf *cgraph,
-	git_commit_graph_writer *w,
-	git_commit_graph_writer_options *opts)
+	git_commit_graph_writer *w)
 {
-	GIT_BUF_WRAP_PRIVATE(cgraph, git_commit_graph__writer_dump, w, opts);
+	GIT_BUF_WRAP_PRIVATE(cgraph, git_commit_graph__writer_dump, w);
 }
 
 int git_commit_graph__writer_dump(
 	git_str *cgraph,
-	git_commit_graph_writer *w,
-	git_commit_graph_writer_options *opts)
+	git_commit_graph_writer *w)
 {
-	/* TODO: support options. */
-	GIT_UNUSED(opts);
 	return commit_graph_write(w, commit_graph_write_buf, cgraph);
 }
diff --git a/src/libgit2/commit_graph.h b/src/libgit2/commit_graph.h
index ecf4379bdb6..a06f3f86219 100644
--- a/src/libgit2/commit_graph.h
+++ b/src/libgit2/commit_graph.h
@@ -156,8 +156,7 @@ struct git_commit_graph_writer {
 
 int git_commit_graph__writer_dump(
 	git_str *cgraph,
-	git_commit_graph_writer *w,
-	git_commit_graph_writer_options *opts);
+	git_commit_graph_writer *w);
 
 /*
  * Returns whether the git_commit_graph_file needs to be reloaded since the
diff --git a/src/libgit2/index.c b/src/libgit2/index.c
index 29d10ef7213..a3142c8bcd9 100644
--- a/src/libgit2/index.c
+++ b/src/libgit2/index.c
@@ -399,6 +399,7 @@ int git_index__open(
 	index = git__calloc(1, sizeof(git_index));
 	GIT_ERROR_CHECK_ALLOC(index);
 
+	GIT_ASSERT_ARG(git_oid_type_is_valid(oid_type));
 	index->oid_type = oid_type;
 
 	if (git_pool_init(&index->tree_pool, 1) < 0)
@@ -441,9 +442,13 @@ int git_index__open(
 }
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-int git_index_open(git_index **index_out, const char *index_path, git_oid_t oid_type)
+int git_index_open(
+	git_index **index_out,
+	const char *index_path,
+	const git_index_options *opts)
 {
-	return git_index__open(index_out, index_path, oid_type);
+	return git_index__open(index_out, index_path,
+		opts && opts->oid_type ? opts->oid_type : GIT_OID_DEFAULT);
 }
 #else
 int git_index_open(git_index **index_out, const char *index_path)
@@ -458,9 +463,10 @@ int git_index__new(git_index **out, git_oid_t oid_type)
 }
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-int git_index_new(git_index **out, git_oid_t oid_type)
+int git_index_new(git_index **out, const git_index_options *opts)
 {
-	return git_index__new(out, oid_type);
+	return git_index__new(out,
+		opts && opts->oid_type ? opts->oid_type : GIT_OID_DEFAULT);
 }
 #else
 int git_index_new(git_index **out)
diff --git a/src/libgit2/indexer.c b/src/libgit2/indexer.c
index 32a37e0670a..e62daacfa51 100644
--- a/src/libgit2/indexer.c
+++ b/src/libgit2/indexer.c
@@ -171,9 +171,12 @@ static int indexer_new(
 	if (in_opts)
 		memcpy(&opts, in_opts, sizeof(opts));
 
+	if (oid_type)
+		GIT_ASSERT_ARG(git_oid_type_is_valid(oid_type));
+
 	idx = git__calloc(1, sizeof(git_indexer));
 	GIT_ERROR_CHECK_ALLOC(idx);
-	idx->oid_type = oid_type;
+	idx->oid_type = oid_type ? oid_type : GIT_OID_DEFAULT;
 	idx->odb = odb;
 	idx->progress_cb = opts.progress_cb;
 	idx->progress_payload = opts.progress_cb_payload;
@@ -233,13 +236,12 @@ static int indexer_new(
 int git_indexer_new(
 	git_indexer **out,
 	const char *prefix,
-	git_oid_t oid_type,
 	git_indexer_options *opts)
 {
 	return indexer_new(
 		out,
 		prefix,
-		oid_type,
+		opts ? opts->oid_type : 0,
 		opts ? opts->mode : 0,
 		opts ? opts->odb : NULL,
 		opts);
diff --git a/src/libgit2/midx.c b/src/libgit2/midx.c
index 0b16af94390..1336ed85f88 100644
--- a/src/libgit2/midx.c
+++ b/src/libgit2/midx.c
@@ -508,20 +508,28 @@ static int packfile__cmp(const void *a_, const void *b_)
 }
 
 int git_midx_writer_new(
-		git_midx_writer **out,
-		const char *pack_dir
+	git_midx_writer **out,
+	const char *pack_dir
 #ifdef GIT_EXPERIMENTAL_SHA256
-		, git_oid_t oid_type
+	, git_midx_writer_options *opts
 #endif
 		)
 {
 	git_midx_writer *w;
+	git_oid_t oid_type;
 
-#ifndef GIT_EXPERIMENTAL_SHA256
-	git_oid_t oid_type = GIT_OID_SHA1;
-#endif
+	GIT_ASSERT_ARG(out && pack_dir);
 
-	GIT_ASSERT_ARG(out && pack_dir && oid_type);
+#ifdef GIT_EXPERIMENTAL_SHA256
+	GIT_ERROR_CHECK_VERSION(opts,
+		GIT_MIDX_WRITER_OPTIONS_VERSION,
+		"git_midx_writer_options");
+
+	oid_type = opts && opts->oid_type ? opts->oid_type : GIT_OID_DEFAULT;
+	GIT_ASSERT_ARG(git_oid_type_is_valid(oid_type));
+#else
+	oid_type = GIT_OID_SHA1;
+#endif
 
 	w = git__calloc(1, sizeof(git_midx_writer));
 	GIT_ERROR_CHECK_ALLOC(w);
diff --git a/src/libgit2/odb_pack.c b/src/libgit2/odb_pack.c
index 96d3a2be476..ef8d35309fe 100644
--- a/src/libgit2/odb_pack.c
+++ b/src/libgit2/odb_pack.c
@@ -743,10 +743,10 @@ static int pack_backend__writepack(struct git_odb_writepack **out,
 
 #ifdef GIT_EXPERIMENTAL_SHA256
 	opts.odb = odb;
+	opts.oid_type = backend->opts.oid_type;
 
 	error = git_indexer_new(&writepack->indexer,
 		backend->pack_folder,
-		backend->opts.oid_type,
 		&opts);
 #else
 	error = git_indexer_new(&writepack->indexer,
@@ -796,13 +796,21 @@ static int pack_backend__writemidx(git_odb_backend *_backend)
 	size_t i;
 	int error = 0;
 
+#ifdef GIT_EXPERIMENTAL_SHA256
+	git_midx_writer_options midx_opts = GIT_MIDX_WRITER_OPTIONS_INIT;
+#endif
+
 	GIT_ASSERT_ARG(_backend);
 
 	backend = (struct pack_backend *)_backend;
 
+#ifdef GIT_EXPERIMENTAL_SHA256
+	midx_opts.oid_type = backend->opts.oid_type;
+#endif
+
 	error = git_midx_writer_new(&w, backend->pack_folder
 #ifdef GIT_EXPERIMENTAL_SHA256
-		, backend->opts.oid_type
+		, &midx_opts
 #endif
 		);
 
diff --git a/src/libgit2/oid.h b/src/libgit2/oid.h
index f25a899a681..9415915fcb2 100644
--- a/src/libgit2/oid.h
+++ b/src/libgit2/oid.h
@@ -66,6 +66,15 @@ GIT_INLINE(size_t) git_oid_hexsize(git_oid_t type)
 	return 0;
 }
 
+GIT_INLINE(bool) git_oid_type_is_valid(git_oid_t type)
+{
+	return (type == GIT_OID_SHA1
+#ifdef GIT_EXPERIMENTAL_SHA256
+	     || type == GIT_OID_SHA256
+#endif
+	);
+}
+
 GIT_INLINE(const char *) git_oid_type_name(git_oid_t type)
 {
 	switch (type) {
diff --git a/src/libgit2/pack-objects.c b/src/libgit2/pack-objects.c
index 298e70aa605..ced98e8c86d 100644
--- a/src/libgit2/pack-objects.c
+++ b/src/libgit2/pack-objects.c
@@ -1442,8 +1442,9 @@ int git_packbuilder_write(
 #ifdef GIT_EXPERIMENTAL_SHA256
 	opts.mode = mode;
 	opts.odb = pb->odb;
+	opts.oid_type = GIT_OID_SHA1;
 
-	error = git_indexer_new(&indexer, path, GIT_OID_SHA1, &opts);
+	error = git_indexer_new(&indexer, path, &opts);
 #else
 	error = git_indexer_new(&indexer, path, mode, pb->odb, &opts);
 #endif
diff --git a/src/libgit2/repository.c b/src/libgit2/repository.c
index d41fa3933ad..82aea517a1c 100644
--- a/src/libgit2/repository.c
+++ b/src/libgit2/repository.c
@@ -335,6 +335,8 @@ int git_repository__new(git_repository **out, git_oid_t oid_type)
 	*out = repo = repository_alloc();
 	GIT_ERROR_CHECK_ALLOC(repo);
 
+	GIT_ASSERT_ARG(git_oid_type_is_valid(oid_type));
+
 	repo->is_bare = 1;
 	repo->is_worktree = 0;
 	repo->oid_type = oid_type;
@@ -343,9 +345,9 @@ int git_repository__new(git_repository **out, git_oid_t oid_type)
 }
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-int git_repository_new(git_repository **out, git_oid_t oid_type)
+int git_repository_new(git_repository **out, git_repository_new_options *opts)
 {
-	return git_repository__new(out, oid_type);
+	return git_repository__new(out, opts && opts->oid_type ? opts->oid_type : GIT_OID_DEFAULT);
 }
 #else
 int git_repository_new(git_repository** out)
@@ -1221,17 +1223,15 @@ int git_repository_open_from_worktree(git_repository **repo_out, git_worktree *w
 	return err;
 }
 
-int git_repository__wrap_odb(
-	git_repository **out,
-	git_odb *odb,
-	git_oid_t oid_type)
+int git_repository_wrap_odb(git_repository **out, git_odb *odb)
 {
 	git_repository *repo;
 
 	repo = repository_alloc();
 	GIT_ERROR_CHECK_ALLOC(repo);
 
-	repo->oid_type = oid_type;
+	GIT_ASSERT(git_oid_type_is_valid(odb->options.oid_type));
+	repo->oid_type = odb->options.oid_type;
 
 	git_repository_set_odb(repo, odb);
 	*out = repo;
@@ -1239,21 +1239,6 @@ int git_repository__wrap_odb(
 	return 0;
 }
 
-#ifdef GIT_EXPERIMENTAL_SHA256
-int git_repository_wrap_odb(
-	git_repository **out,
-	git_odb *odb,
-	git_oid_t oid_type)
-{
-	return git_repository__wrap_odb(out, odb, oid_type);
-}
-#else
-int git_repository_wrap_odb(git_repository **out, git_odb *odb)
-{
-	return git_repository__wrap_odb(out, odb, GIT_OID_DEFAULT);
-}
-#endif
-
 int git_repository_discover(
 	git_buf *out,
 	const char *start_path,
diff --git a/src/libgit2/repository.h b/src/libgit2/repository.h
index 79e087bfa93..fbf143894e6 100644
--- a/src/libgit2/repository.h
+++ b/src/libgit2/repository.h
@@ -199,11 +199,6 @@ int git_repository_index__weakptr(git_index **out, git_repository *repo);
 int git_repository_grafts__weakptr(git_grafts **out, git_repository *repo);
 int git_repository_shallow_grafts__weakptr(git_grafts **out, git_repository *repo);
 
-int git_repository__wrap_odb(
-	git_repository **out,
-	git_odb *odb,
-	git_oid_t oid_type);
-
 /*
  * Configuration map cache
  *
diff --git a/tests/libgit2/attr/repo.c b/tests/libgit2/attr/repo.c
index 747715b51fa..793c1a7d041 100644
--- a/tests/libgit2/attr/repo.c
+++ b/tests/libgit2/attr/repo.c
@@ -318,7 +318,7 @@ void test_attr_repo__inmemory_repo_without_index(void)
 
 	/* setup bare in-memory repo without index */
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_repository_new(&inmemory, GIT_OID_SHA1));
+	cl_git_pass(git_repository_new(&inmemory, NULL));
 #else
 	cl_git_pass(git_repository_new(&inmemory));
 #endif
diff --git a/tests/libgit2/graph/commitgraph.c b/tests/libgit2/graph/commitgraph.c
index 53869d61db0..363806bd9e9 100644
--- a/tests/libgit2/graph/commitgraph.c
+++ b/tests/libgit2/graph/commitgraph.c
@@ -105,18 +105,19 @@ void test_graph_commitgraph__writer(void)
 	cl_git_pass(git_str_joinpath(&path, git_repository_path(repo), "objects/info"));
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_commit_graph_writer_new(&w, git_str_cstr(&path), GIT_OID_SHA1));
-#else
-	cl_git_pass(git_commit_graph_writer_new(&w, git_str_cstr(&path)));
+	opts.oid_type = GIT_OID_SHA1;
 #endif
 
+	cl_git_pass(git_commit_graph_writer_new(&w, git_str_cstr(&path), &opts));
+
 	/* This is equivalent to `git commit-graph write --reachable`. */
 	cl_git_pass(git_revwalk_new(&walk, repo));
 	cl_git_pass(git_revwalk_push_glob(walk, "refs/*"));
 	cl_git_pass(git_commit_graph_writer_add_revwalk(w, walk));
 	git_revwalk_free(walk);
 
-	cl_git_pass(git_commit_graph_writer_dump(&cgraph, w, &opts));
+	cl_git_pass(git_commit_graph_writer_dump(&cgraph, w));
+
 	cl_git_pass(git_str_joinpath(&path, git_repository_path(repo), "objects/info/commit-graph"));
 	cl_git_pass(git_futils_readbuffer(&expected_cgraph, git_str_cstr(&path)));
 
@@ -136,12 +137,16 @@ void test_graph_commitgraph__validate(void)
 	struct git_commit_graph *cgraph;
 	git_str objects_dir = GIT_STR_INIT;
 
+#ifdef GIT_EXPERIMENTAL_SHA256
+	git_commit_graph_open_options opts = GIT_COMMIT_GRAPH_OPEN_OPTIONS_INIT;
+#endif
+
 	cl_git_pass(git_repository_open(&repo, cl_fixture("testrepo.git")));
 	cl_git_pass(git_str_joinpath(&objects_dir, git_repository_path(repo), "objects"));
 
 	/* git_commit_graph_open() calls git_commit_graph_validate() */
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_commit_graph_open(&cgraph, git_str_cstr(&objects_dir), GIT_OID_SHA1));
+	cl_git_pass(git_commit_graph_open(&cgraph, git_str_cstr(&objects_dir), &opts));
 #else
 	cl_git_pass(git_commit_graph_open(&cgraph, git_str_cstr(&objects_dir)));
 #endif
@@ -157,6 +162,10 @@ void test_graph_commitgraph__validate_corrupt(void)
 	struct git_commit_graph *cgraph;
 	int fd = -1;
 
+#ifdef GIT_EXPERIMENTAL_SHA256
+	git_commit_graph_open_options opts = GIT_COMMIT_GRAPH_OPEN_OPTIONS_INIT;
+#endif
+
 	cl_fixture_sandbox("testrepo.git");
 	cl_git_pass(git_repository_open(&repo, cl_git_sandbox_path(1, "testrepo.git", NULL)));
 
@@ -168,7 +177,7 @@ void test_graph_commitgraph__validate_corrupt(void)
 
 	/* git_commit_graph_open() calls git_commit_graph_validate() */
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_fail(git_commit_graph_open(&cgraph, cl_git_sandbox_path(1, "testrepo.git", "objects", NULL), GIT_OID_SHA1));
+	cl_git_fail(git_commit_graph_open(&cgraph, cl_git_sandbox_path(1, "testrepo.git", "objects", NULL), &opts));
 #else
 	cl_git_fail(git_commit_graph_open(&cgraph, cl_git_sandbox_path(1, "testrepo.git", "objects", NULL)));
 #endif
diff --git a/tests/libgit2/network/remote/local.c b/tests/libgit2/network/remote/local.c
index f69502c7b15..9f3c8b61179 100644
--- a/tests/libgit2/network/remote/local.c
+++ b/tests/libgit2/network/remote/local.c
@@ -471,10 +471,14 @@ void test_network_remote_local__anonymous_remote_inmemory_repo(void)
 	git_repository *inmemory;
 	git_remote *remote;
 
+#ifdef GIT_EXPERIMENTAL_SHA256
+	git_repository_new_options repo_opts = GIT_REPOSITORY_NEW_OPTIONS_INIT;
+#endif
+
 	git_str_sets(&file_path_buf, cl_git_path_url(cl_fixture("testrepo.git")));
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_repository_new(&inmemory, GIT_OID_SHA1));
+	cl_git_pass(git_repository_new(&inmemory, &repo_opts));
 #else
 	cl_git_pass(git_repository_new(&inmemory));
 #endif
diff --git a/tests/libgit2/odb/backend/loose.c b/tests/libgit2/odb/backend/loose.c
index 02227945d71..f5a0b4f5caf 100644
--- a/tests/libgit2/odb/backend/loose.c
+++ b/tests/libgit2/odb/backend/loose.c
@@ -21,7 +21,7 @@ void test_odb_backend_loose__initialize(void)
 
 	cl_git_pass(git_odb__new(&_odb, NULL));
 	cl_git_pass(git_odb_add_backend(_odb, backend, 10));
-	cl_git_pass(git_repository__wrap_odb(&_repo, _odb, GIT_OID_SHA1));
+	cl_git_pass(git_repository_wrap_odb(&_repo, _odb));
 }
 
 void test_odb_backend_loose__cleanup(void)
diff --git a/tests/libgit2/odb/backend/mempack.c b/tests/libgit2/odb/backend/mempack.c
index 84449090a06..462a1d333a6 100644
--- a/tests/libgit2/odb/backend/mempack.c
+++ b/tests/libgit2/odb/backend/mempack.c
@@ -15,7 +15,7 @@ void test_odb_backend_mempack__initialize(void)
 	cl_git_pass(git_mempack_new(&_backend));
 	cl_git_pass(git_odb__new(&_odb, NULL));
 	cl_git_pass(git_odb_add_backend(_odb, _backend, 10));
-	cl_git_pass(git_repository__wrap_odb(&_repo, _odb, GIT_OID_SHA1));
+	cl_git_pass(git_repository_wrap_odb(&_repo, _odb));
 }
 
 void test_odb_backend_mempack__cleanup(void)
diff --git a/tests/libgit2/odb/backend/nobackend.c b/tests/libgit2/odb/backend/nobackend.c
index a81e5857715..e8af9a6d6fa 100644
--- a/tests/libgit2/odb/backend/nobackend.c
+++ b/tests/libgit2/odb/backend/nobackend.c
@@ -12,7 +12,11 @@ void test_odb_backend_nobackend__initialize(void)
 	git_refdb *refdb;
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_repository_new(&_repo, GIT_OID_SHA1));
+	git_repository_new_options repo_opts = GIT_REPOSITORY_NEW_OPTIONS_INIT;
+
+	repo_opts.oid_type = GIT_OID_SHA1;
+
+	cl_git_pass(git_repository_new(&_repo, &repo_opts));
 #else
 	cl_git_pass(git_repository_new(&_repo));
 #endif
diff --git a/tests/libgit2/pack/indexer.c b/tests/libgit2/pack/indexer.c
index 9722decafc0..023eb5da795 100644
--- a/tests/libgit2/pack/indexer.c
+++ b/tests/libgit2/pack/indexer.c
@@ -101,7 +101,7 @@ void test_pack_indexer__out_of_order(void)
 	git_indexer_progress stats = { 0 };
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_indexer_new(&idx, ".", GIT_OID_SHA1, NULL));
+	cl_git_pass(git_indexer_new(&idx, ".", NULL));
 #else
 	cl_git_pass(git_indexer_new(&idx, ".", 0, NULL, NULL));
 #endif
@@ -123,7 +123,7 @@ void test_pack_indexer__missing_trailer(void)
 	git_indexer_progress stats = { 0 };
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_indexer_new(&idx, ".", GIT_OID_SHA1, NULL));
+	cl_git_pass(git_indexer_new(&idx, ".", NULL));
 #else
 	cl_git_pass(git_indexer_new(&idx, ".", 0, NULL, NULL));
 #endif
@@ -144,7 +144,7 @@ void test_pack_indexer__leaky(void)
 	git_indexer_progress stats = { 0 };
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_indexer_new(&idx, ".", GIT_OID_SHA1, NULL));
+	cl_git_pass(git_indexer_new(&idx, ".", NULL));
 #else
 	cl_git_pass(git_indexer_new(&idx, ".", 0, NULL, NULL));
 #endif
@@ -178,7 +178,7 @@ void test_pack_indexer__fix_thin(void)
 
 #ifdef GIT_EXPERIMENTAL_SHA256
 	opts.odb = odb;
-	cl_git_pass(git_indexer_new(&idx, ".", GIT_OID_SHA1, &opts));
+	cl_git_pass(git_indexer_new(&idx, ".", &opts));
 #else
 	cl_git_pass(git_indexer_new(&idx, ".", 0, odb, &opts));
 #endif
@@ -215,7 +215,7 @@ void test_pack_indexer__fix_thin(void)
 		cl_git_pass(p_stat(name, &st));
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-		cl_git_pass(git_indexer_new(&idx, ".", GIT_OID_SHA1, NULL));
+		cl_git_pass(git_indexer_new(&idx, ".", NULL));
 #else
 		cl_git_pass(git_indexer_new(&idx, ".", 0, NULL, NULL));
 #endif
@@ -255,7 +255,8 @@ void test_pack_indexer__corrupt_length(void)
 
 #ifdef GIT_EXPERIMENTAL_SHA256
 	opts.odb = odb;
-	cl_git_pass(git_indexer_new(&idx, ".", GIT_OID_SHA1, &opts));
+	opts.oid_type = GIT_OID_SHA1;
+	cl_git_pass(git_indexer_new(&idx, ".", &opts));
 #else
 	cl_git_pass(git_indexer_new(&idx, ".", 0, odb, &opts));
 #endif
@@ -281,7 +282,7 @@ void test_pack_indexer__incomplete_pack_fails_with_strict(void)
 	opts.verify = 1;
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_indexer_new(&idx, ".", GIT_OID_SHA1, &opts));
+	cl_git_pass(git_indexer_new(&idx, ".", &opts));
 #else
 	cl_git_pass(git_indexer_new(&idx, ".", 0, NULL, &opts));
 #endif
@@ -306,7 +307,7 @@ void test_pack_indexer__out_of_order_with_connectivity_checks(void)
 	opts.verify = 1;
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_indexer_new(&idx, ".", GIT_OID_SHA1, &opts));
+	cl_git_pass(git_indexer_new(&idx, ".", &opts));
 #else
 	cl_git_pass(git_indexer_new(&idx, ".", 0, NULL, &opts));
 #endif
@@ -354,7 +355,7 @@ void test_pack_indexer__no_tmp_files(void)
 	cl_assert(git_str_len(&first_tmp_file) == 0);
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_indexer_new(&idx, ".", GIT_OID_SHA1, NULL));
+	cl_git_pass(git_indexer_new(&idx, ".", NULL));
 #else
 	cl_git_pass(git_indexer_new(&idx, ".", 0, NULL, NULL));
 #endif
diff --git a/tests/libgit2/pack/midx.c b/tests/libgit2/pack/midx.c
index 4c4dfc51178..d7180c47898 100644
--- a/tests/libgit2/pack/midx.c
+++ b/tests/libgit2/pack/midx.c
@@ -59,7 +59,7 @@ void test_pack_midx__writer(void)
 	cl_git_pass(git_str_joinpath(&path, git_repository_path(repo), "objects/pack"));
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_midx_writer_new(&w, git_str_cstr(&path), GIT_OID_SHA1));
+	cl_git_pass(git_midx_writer_new(&w, git_str_cstr(&path), NULL));
 #else
 	cl_git_pass(git_midx_writer_new(&w, git_str_cstr(&path)));
 #endif
diff --git a/tests/libgit2/pack/packbuilder.c b/tests/libgit2/pack/packbuilder.c
index 05dea29d10e..2c598b6ee94 100644
--- a/tests/libgit2/pack/packbuilder.c
+++ b/tests/libgit2/pack/packbuilder.c
@@ -102,7 +102,7 @@ void test_pack_packbuilder__create_pack(void)
 	seed_packbuilder();
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_indexer_new(&_indexer, ".", GIT_OID_SHA1, NULL));
+	cl_git_pass(git_indexer_new(&_indexer, ".", NULL));
 #else
 	cl_git_pass(git_indexer_new(&_indexer, ".", 0, NULL, NULL));
 #endif
@@ -261,7 +261,7 @@ void test_pack_packbuilder__foreach(void)
 	seed_packbuilder();
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_indexer_new(&idx, ".", GIT_OID_SHA1, NULL));
+	cl_git_pass(git_indexer_new(&idx, ".", NULL));
 #else
 	cl_git_pass(git_indexer_new(&idx, ".", 0, NULL, NULL));
 #endif
@@ -285,7 +285,7 @@ void test_pack_packbuilder__foreach_with_cancel(void)
 	seed_packbuilder();
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_indexer_new(&idx, ".", GIT_OID_SHA1, NULL));
+	cl_git_pass(git_indexer_new(&idx, ".", NULL));
 #else
 	cl_git_pass(git_indexer_new(&idx, ".", 0, NULL, NULL));
 #endif
diff --git a/tests/libgit2/refs/iterator.c b/tests/libgit2/refs/iterator.c
index 020ee01a484..a46db629085 100644
--- a/tests/libgit2/refs/iterator.c
+++ b/tests/libgit2/refs/iterator.c
@@ -129,7 +129,7 @@ void test_refs_iterator__empty(void)
 	git_repository *empty;
 
 	cl_git_pass(git_odb__new(&odb, NULL));
-	cl_git_pass(git_repository__wrap_odb(&empty, odb, GIT_OID_SHA1));
+	cl_git_pass(git_repository_wrap_odb(&empty, odb));
 
 	cl_git_pass(git_reference_iterator_new(&iter, empty));
 	cl_assert_equal_i(GIT_ITEROVER, git_reference_next(&ref, iter));
diff --git a/tests/libgit2/repo/new.c b/tests/libgit2/repo/new.c
index aaa917a4aba..5136e60b09d 100644
--- a/tests/libgit2/repo/new.c
+++ b/tests/libgit2/repo/new.c
@@ -6,7 +6,11 @@ void test_repo_new__has_nothing(void)
 	git_repository *repo;
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_repository_new(&repo, GIT_OID_SHA1));
+	git_repository_new_options repo_opts = GIT_REPOSITORY_NEW_OPTIONS_INIT;
+
+	repo_opts.oid_type = GIT_OID_SHA1;
+
+	cl_git_pass(git_repository_new(&repo, &repo_opts));
 #else
 	cl_git_pass(git_repository_new(&repo));
 #endif
@@ -21,7 +25,11 @@ void test_repo_new__is_bare_until_workdir_set(void)
 	git_repository *repo;
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_repository_new(&repo, GIT_OID_SHA1));
+	git_repository_new_options repo_opts = GIT_REPOSITORY_NEW_OPTIONS_INIT;
+
+	repo_opts.oid_type = GIT_OID_SHA1;
+
+	cl_git_pass(git_repository_new(&repo, &repo_opts));
 #else
 	cl_git_pass(git_repository_new(&repo));
 #endif
@@ -38,7 +46,11 @@ void test_repo_new__sha1(void)
 	git_repository *repo;
 
 #ifdef GIT_EXPERIMENTAL_SHA256
-	cl_git_pass(git_repository_new(&repo, GIT_OID_SHA1));
+	git_repository_new_options repo_opts = GIT_REPOSITORY_NEW_OPTIONS_INIT;
+
+	repo_opts.oid_type = GIT_OID_SHA1;
+
+	cl_git_pass(git_repository_new(&repo, &repo_opts));
 #else
 	cl_git_pass(git_repository_new(&repo));
 #endif
@@ -53,8 +65,11 @@ void test_repo_new__sha256(void)
 	cl_skip();
 #else
 	git_repository *repo;
+	git_repository_new_options repo_opts = GIT_REPOSITORY_NEW_OPTIONS_INIT;
+
+	repo_opts.oid_type = GIT_OID_SHA256;
 
-	cl_git_pass(git_repository_new(&repo, GIT_OID_SHA256));
+	cl_git_pass(git_repository_new(&repo, &repo_opts));
 	cl_assert_equal_i(GIT_OID_SHA256, git_repository_oid_type(repo));
 
 	git_repository_free(repo);