diff --git a/mypy/checkexpr.py b/mypy/checkexpr.py
index fba6caec4072..e4b50b87b1f2 100644
--- a/mypy/checkexpr.py
+++ b/mypy/checkexpr.py
@@ -4230,6 +4230,10 @@ def infer_lambda_type_using_context(
         callable_ctx = get_proper_type(replace_meta_vars(ctx, ErasedType()))
         assert isinstance(callable_ctx, CallableType)
 
+        # The callable_ctx may have a fallback of builtins.type if the context
+        # is a constructor -- but this fallback doesn't make sense for lambdas.
+        callable_ctx = callable_ctx.copy_modified(fallback=self.named_type("builtins.function"))
+
         if callable_ctx.type_guard is not None:
             # Lambda's return type cannot be treated as a `TypeGuard`,
             # because it is implicit. And `TypeGuard`s must be explicit.
diff --git a/test-data/unit/check-inference.test b/test-data/unit/check-inference.test
index c09424138e49..1e6d947d6113 100644
--- a/test-data/unit/check-inference.test
+++ b/test-data/unit/check-inference.test
@@ -1276,6 +1276,21 @@ class A:
 def h(x: Callable[[], int]) -> None:
     pass
 
+[case testLambdaJoinWithDynamicConstructor]
+from typing import Any, Union
+
+class Wrapper:
+    def __init__(self, x: Any) -> None: ...
+
+def f(cond: bool) -> Any:
+    f = Wrapper if cond else lambda x: x
+    reveal_type(f)  # N: Revealed type is "def (x: Any) -> Any"
+    return f(3)
+
+def g(cond: bool) -> Any:
+    f = lambda x: x if cond else Wrapper
+    reveal_type(f)  # N: Revealed type is "def (x: Any) -> Any"
+    return f(3)
 
 -- Boolean operators
 -- -----------------