diff --git a/commit-graph.c b/commit-graph.c
index c4eaedf4e5..cee2caab5c 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -62,6 +62,9 @@ extern int read_replace_refs;
 
 static int commit_graph_compatible(struct repository *r)
 {
+	if (!r->gitdir)
+		return 0;
+
 	if (read_replace_refs) {
 		prepare_replace_object(r);
 		if (hashmap_get_size(&r->objects->replace_map->map))