diff --git a/Omen/OmenSync.lua b/Omen/OmenSync.lua
index 40de513..5c8a3b1 100644
--- a/Omen/OmenSync.lua
+++ b/Omen/OmenSync.lua
@@ -110,6 +110,12 @@ end
 -- Receiver
 -- ---------------------------------------------------------------------------
 
+-- Register the prefix so CHAT_MSG_ADDON fires for our messages on 3.3.5.
+-- Without this, incoming OMSYNC packets are silently discarded by the client.
+if RegisterAddonMessagePrefix then
+    RegisterAddonMessagePrefix(PREFIX)
+end
+
 local f = CreateFrame("Frame")
 f:RegisterEvent("CHAT_MSG_ADDON")
 f:RegisterEvent("PLAYER_LEAVING_WORLD")