diff --git a/src/git2/object.h b/src/git2/object.h
index 084d11177..128c9faf5 100644
--- a/src/git2/object.h
+++ b/src/git2/object.h
@@ -66,7 +66,7 @@ GIT_EXTERN(int) git_object_write(git_object *object);
  * @param obj the repository object
  * @return the SHA1 id
  */
-GIT_EXTERN(const git_oid *) git_object_id(git_object *obj);
+GIT_EXTERN(const git_oid *) git_object_id(const git_object *obj);
 
 /**
  * Get the object type of an object
@@ -74,7 +74,7 @@ GIT_EXTERN(const git_oid *) git_object_id(git_object *obj);
  * @param obj the repository object
  * @return the object's type
  */
-GIT_EXTERN(git_otype) git_object_type(git_object *obj);
+GIT_EXTERN(git_otype) git_object_type(const git_object *obj);
 
 /**
  * Get the repository that owns this object
@@ -82,7 +82,7 @@ GIT_EXTERN(git_otype) git_object_type(git_object *obj);
  * @param obj the object
  * @return the repository who owns this object
  */
-GIT_EXTERN(git_repository *) git_object_owner(git_object *obj);
+GIT_EXTERN(git_repository *) git_object_owner(const git_object *obj);
 
 /**
  * Free a reference to one of the objects in the repository.
diff --git a/src/object.c b/src/object.c
index dd84cb5d7..c53a3acae 100644
--- a/src/object.c
+++ b/src/object.c
@@ -283,7 +283,7 @@ void git_object_free(git_object *object)
 	}
 }
 
-const git_oid *git_object_id(git_object *obj)
+const git_oid *git_object_id(const git_object *obj)
 {
 	assert(obj);
 
@@ -293,13 +293,13 @@ const git_oid *git_object_id(git_object *obj)
 	return &obj->id;
 }
 
-git_otype git_object_type(git_object *obj)
+git_otype git_object_type(const git_object *obj)
 {
 	assert(obj);
 	return obj->source.raw.type;
 }
 
-git_repository *git_object_owner(git_object *obj)
+git_repository *git_object_owner(const git_object *obj)
 {
 	assert(obj);
 	return obj->repo;