diff --git a/libfwupd/fwupd-remote.c b/libfwupd/fwupd-remote.c
index b090b013b..ce3114418 100644
--- a/libfwupd/fwupd-remote.c
+++ b/libfwupd/fwupd-remote.c
@@ -1148,7 +1148,7 @@ fwupd_remote_load_signature_jcat(FwupdRemote *self, JcatFile *jcat_file, GError
 
 	/* replace the URI if required */
 	baseuri = g_path_get_dirname(priv->metadata_uri);
-	metadata_uri = g_build_filename(baseuri, id, NULL);
+	metadata_uri = g_build_path("/", baseuri, id, NULL);
 	if (g_strcmp0(metadata_uri, priv->metadata_uri) != 0) {
 		g_debug("changing metadata URI from %s to %s", priv->metadata_uri, metadata_uri);
 		g_free(priv->metadata_uri);