diff --git a/proposals/xxxx-webxdc.md b/proposals/4211-webxdc.md
similarity index 99%
rename from proposals/xxxx-webxdc.md
rename to proposals/4211-webxdc.md
index 4be1c79f5..43b0e9bda 100644
--- a/proposals/xxxx-webxdc.md
+++ b/proposals/4211-webxdc.md
@@ -1,4 +1,4 @@
-# MSCXXXX: WebXDC on Matrix
+# MSC4211: WebXDC on Matrix
 
 
 In Matrix, users may want to send each other interactive content (for example a game