diff --git a/README b/README
index 6095b272e6dd3cb4f2e63b0bd19088660e465ba3..039b03a9c3cbdc5a0588835bac6a700d604121ed 100644
--- a/README
+++ b/README
@@ -56,6 +56,8 @@ Xfwm is compliant with the following specifications from the freedesktop.org
     NET_WM_STATE_STICKY
     NET_WM_STRUT
     NET_WM_STRUT_PARTIAL
+    NET_WM_SYNC_REQUEST
+    NET_WM_SYNC_REQUEST_COUNTER
     NET_WM_USER_TIME
     NET_WM_WINDOW_TYPE
     NET_WM_WINDOW_TYPE_DESKTOP