diff --git a/builtin/difftool.c b/builtin/difftool.c
index ca1b0890659b52..40e971e2259db4 100644
--- a/builtin/difftool.c
+++ b/builtin/difftool.c
@@ -376,7 +376,8 @@ static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 	struct checkout lstate, rstate;
 	int err = 0;
 	struct child_process cmd = CHILD_PROCESS_INIT;
-	struct hashmap wt_modified, tmp_modified;
+	struct hashmap wt_modified = HASHMAP_INIT(path_entry_cmp, NULL);
+	struct hashmap tmp_modified = HASHMAP_INIT(path_entry_cmp, NULL);
 	int indices_loaded = 0;
 
 	workdir = repo_get_work_tree(the_repository);
@@ -601,9 +602,6 @@ static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 	 * in the common case of --symlinks and the difftool updating
 	 * files through the symlink.
 	 */
-	hashmap_init(&wt_modified, path_entry_cmp, NULL, wtindex.cache_nr);
-	hashmap_init(&tmp_modified, path_entry_cmp, NULL, wtindex.cache_nr);
-
 	for (i = 0; i < wtindex.cache_nr; i++) {
 		struct hashmap_entry dummy;
 		const char *name = wtindex.cache[i]->name;
diff --git a/t/t7800-difftool.sh b/t/t7800-difftool.sh
index f67b9345b8a013..fcaa1748e4a8e7 100755
--- a/t/t7800-difftool.sh
+++ b/t/t7800-difftool.sh
@@ -666,6 +666,10 @@ run_dir_diff_test 'difftool --dir-diff syncs worktree without unstaged change' '
 	test_cmp expect file
 '
 
+run_dir_diff_test 'difftool --dir-diff with no diff' '
+	git difftool -d main main
+'
+
 write_script modify-file <<\EOF
 echo "new content" >file
 EOF