diff --git a/gio/gdbusauthmechanismexternal.c b/gio/gdbusauthmechanismexternal.c
index a18c69729..ec23dde09 100644
--- a/gio/gdbusauthmechanismexternal.c
+++ b/gio/gdbusauthmechanismexternal.c
@@ -337,7 +337,7 @@ mechanism_client_initiate (GDBusAuthMechanism   *mechanism,
   m->priv->is_client = TRUE;
   m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_ACCEPTED;
 
-  *out_initial_response_len = -1;
+  *out_initial_response_len = 0;
 
   credentials = _g_dbus_auth_mechanism_get_credentials (mechanism);
   g_assert (credentials != NULL);
diff --git a/gio/gdbusauthmechanismsha1.c b/gio/gdbusauthmechanismsha1.c
index 585694277..5387659e6 100644
--- a/gio/gdbusauthmechanismsha1.c
+++ b/gio/gdbusauthmechanismsha1.c
@@ -1118,7 +1118,7 @@ mechanism_client_initiate (GDBusAuthMechanism   *mechanism,
   m->priv->is_client = TRUE;
   m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_WAITING_FOR_DATA;
 
-  *out_initial_response_len = -1;
+  *out_initial_response_len = 0;
 
 #ifdef G_OS_UNIX
   initial_response = g_strdup_printf ("%" G_GINT64_FORMAT, (gint64) getuid ());