diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index 07a1935cbe..d06e2fe265 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -3193,13 +3193,13 @@ static void append_fetch_remotes(struct strbuf *msg, const char *git_dir_path)
 
 static int add_submodule(const struct add_data *add_data)
 {
-	char *submod_gitdir_path;
 	struct module_clone_data clone_data = MODULE_CLONE_DATA_INIT;
 	struct string_list reference = STRING_LIST_INIT_NODUP;
 	int ret = -1;
 
 	/* perhaps the path already exists and is already a git repo, else clone it */
 	if (is_directory(add_data->sm_path)) {
+		char *submod_gitdir_path;
 		struct strbuf sm_path = STRBUF_INIT;
 		strbuf_addstr(&sm_path, add_data->sm_path);
 		submod_gitdir_path = xstrfmt("%s/.git", add_data->sm_path);
@@ -3213,10 +3213,11 @@ static int add_submodule(const struct add_data *add_data)
 		free(submod_gitdir_path);
 	} else {
 		struct child_process cp = CHILD_PROCESS_INIT;
+		struct strbuf submod_gitdir = STRBUF_INIT;
 
-		submod_gitdir_path = xstrfmt(".git/modules/%s", add_data->sm_name);
+		submodule_name_to_gitdir(&submod_gitdir, the_repository, add_data->sm_name);
 
-		if (is_directory(submod_gitdir_path)) {
+		if (is_directory(submod_gitdir.buf)) {
 			if (!add_data->force) {
 				struct strbuf msg = STRBUF_INIT;
 				char *die_msg;
@@ -3225,8 +3226,8 @@ static int add_submodule(const struct add_data *add_data)
 						    "locally with remote(s):\n"),
 					    add_data->sm_name);
 
-				append_fetch_remotes(&msg, submod_gitdir_path);
-				free(submod_gitdir_path);
+				append_fetch_remotes(&msg, submod_gitdir.buf);
+				strbuf_release(&submod_gitdir);
 
 				strbuf_addf(&msg, _("If you want to reuse this local git "
 						    "directory instead of cloning again from\n"
@@ -3244,7 +3245,7 @@ static int add_submodule(const struct add_data *add_data)
 					 "submodule '%s'\n"), add_data->sm_name);
 			}
 		}
-		free(submod_gitdir_path);
+		strbuf_release(&submod_gitdir);
 
 		clone_data.prefix = add_data->prefix;
 		clone_data.path = add_data->sm_path;