diff --git a/alloc.c b/alloc.c
index e7aa81b7aa..1c64c4dd16 100644
--- a/alloc.c
+++ b/alloc.c
@@ -99,18 +99,23 @@ void *alloc_object_node(struct repository *r)
 	return obj;
 }
 
-unsigned int alloc_commit_index(struct repository *r)
+static unsigned int alloc_commit_index(struct repository *r)
 {
 	return r->parsed_objects->commit_count++;
 }
 
+void init_commit_node(struct repository *r, struct commit *c)
+{
+	c->object.type = OBJ_COMMIT;
+	c->index = alloc_commit_index(r);
+	c->graph_pos = COMMIT_NOT_FROM_GRAPH;
+	c->generation = GENERATION_NUMBER_INFINITY;
+}
+
 void *alloc_commit_node(struct repository *r)
 {
 	struct commit *c = alloc_node(r->parsed_objects->commit_state, sizeof(struct commit));
-	c->object.type = OBJ_COMMIT;
-	c->index = alloc_commit_index(r);
-	c->graph_pos = COMMIT_NOT_FROM_GRAPH;
-	c->generation = GENERATION_NUMBER_INFINITY;
+	init_commit_node(r, c);
 	return c;
 }
 
diff --git a/alloc.h b/alloc.h
index ba356ed847..ed1071c11e 100644
--- a/alloc.h
+++ b/alloc.h
@@ -9,11 +9,11 @@ struct repository;
 
 void *alloc_blob_node(struct repository *r);
 void *alloc_tree_node(struct repository *r);
+void init_commit_node(struct repository *r, struct commit *c);
 void *alloc_commit_node(struct repository *r);
 void *alloc_tag_node(struct repository *r);
 void *alloc_object_node(struct repository *r);
 void alloc_report(struct repository *r);
-unsigned int alloc_commit_index(struct repository *r);
 
 struct alloc_state *allocate_alloc_state(void);
 void clear_alloc_state(struct alloc_state *s);
diff --git a/object.c b/object.c
index 51c4594515..675cb8902b 100644
--- a/object.c
+++ b/object.c
@@ -164,8 +164,9 @@ void *object_as_type(struct repository *r, struct object *obj, enum object_type
 		return obj;
 	else if (obj->type == OBJ_NONE) {
 		if (type == OBJ_COMMIT)
-			((struct commit *)obj)->index = alloc_commit_index(r);
-		obj->type = type;
+			init_commit_node(r, (struct commit *) obj);
+		else
+			obj->type = type;
 		return obj;
 	}
 	else {