return NULL;
                }
        } else {
-               sanitized = xstrfmt("%.*s%s", len, prefix, path);
+               sanitized = xstrfmt("%.*s%s", len, len ? prefix : "", path);
                if (remaining_prefix)
                        *remaining_prefix = len;
                if (normalize_path_copy_len(sanitized, sanitized, remaining_prefix)) {