diff --git a/lib/commit.js b/lib/commit.js
index 710902bc8..63e7d7257 100644
--- a/lib/commit.js
+++ b/lib/commit.js
@@ -175,7 +175,7 @@ Commit.prototype.parents = function() {
 Commit.prototype.getDiff = function(callback) {
   var commit = this;
 
-  return commit.getParents().then(function(parents) {
+  return commit.getParents(1).then(function(parents) {
     var diffs = parents.map(function(parent) {
       return parent.getTree().then(function(parentTree) {
         return commit.getTree().then(function(thisTree) {