diff --git a/builtin/commit.c b/builtin/commit.c
index e588bc6..32ffc7b 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -347,7 +347,7 @@ static const char *prepare_index(int argc, const char **argv, const char *prefix
 		die(_("index file corrupt"));
 
 	if (interactive) {
-		char *old_index_env = NULL;
+		char *old_index_env = NULL, *old_repo_index_file;
 		hold_locked_index(&index_lock, LOCK_DIE_ON_ERROR);
 
 		refresh_cache_or_die(refresh_flags);
@@ -355,12 +355,16 @@ static const char *prepare_index(int argc, const char **argv, const char *prefix
 		if (write_locked_index(&the_index, &index_lock, 0))
 			die(_("unable to create temporary index"));
 
+		old_repo_index_file = the_repository->index_file;
+		the_repository->index_file =
+			(char *)get_lock_file_path(&index_lock);
 		old_index_env = xstrdup_or_null(getenv(INDEX_ENVIRONMENT));
-		setenv(INDEX_ENVIRONMENT, get_lock_file_path(&index_lock), 1);
+		setenv(INDEX_ENVIRONMENT, the_repository->index_file, 1);
 
 		if (interactive_add(argc, argv, prefix, patch_interactive) != 0)
 			die(_("interactive add failed"));
 
+		the_repository->index_file = old_repo_index_file;
 		if (old_index_env && *old_index_env)
 			setenv(INDEX_ENVIRONMENT, old_index_env, 1);
 		else