diff --git a/include/git2/tree.h b/include/git2/tree.h
index a3c601291..3085b3fd6 100644
--- a/include/git2/tree.h
+++ b/include/git2/tree.h
@@ -214,8 +214,9 @@ GIT_EXTERN(void) git_tree_entry_set_name(git_tree_entry *entry, const char *name
  *
  * @param entry Entry object which will be modified
  * @param oid new attributes for the entry
+ * @return 0 if the attributes were properly set; error code otherwise
  */
-GIT_EXTERN(int) git_tree_entry_set_attributes(git_tree_entry *entry, int attr);
+GIT_EXTERN(int) git_tree_entry_set_attributes(git_tree_entry *entry, unsigned int attr);
 
 /** @} */
 GIT_END_DECL
diff --git a/src/tree.c b/src/tree.c
index 16824f9d2..702cccbce 100644
--- a/src/tree.c
+++ b/src/tree.c
@@ -107,7 +107,7 @@ const git_oid *git_tree_id(git_tree *c)
 	return git_object_id((git_object *)c);
 }
 
-int git_tree_entry_set_attributes(git_tree_entry *entry, int attr)
+int git_tree_entry_set_attributes(git_tree_entry *entry, unsigned int attr)
 {
 	assert(entry && entry->owner);