diff --git a/read-cache.c b/read-cache.c
index 9aaba14073672c..ebe88cd039dd1c 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -2405,7 +2405,8 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 	if (!istate->repo)
 		istate->repo = the_repository;
 	prepare_repo_settings(istate->repo);
-	if (istate->repo->settings.command_requires_full_index)
+	if (!istate->repo->settings.sparse_index ||
+	    istate->repo->settings.command_requires_full_index)
 		ensure_full_index(istate);
 
 	return istate->cache_nr;