diff --git a/karax/jwebsockets.nim b/karax/jwebsockets.nim
index c662ad1..2b1412e 100644
--- a/karax/jwebsockets.nim
+++ b/karax/jwebsockets.nim
@@ -6,6 +6,7 @@ type
 
   WebSocket* {.importc.} = ref object
     onmessage*: proc (e: MessageEvent)
+    onopen*: proc (e: MessageEvent)
 
 proc newWebSocket*(url, key: cstring): WebSocket
   {.importcpp: "new WebSocket(@)".}