diff --git a/server/internal/websocket/handler.go b/server/internal/websocket/handler.go
index 431a1691..bdd0d4ee 100644
--- a/server/internal/websocket/handler.go
+++ b/server/internal/websocket/handler.go
@@ -54,7 +54,7 @@ func (h *MessageHandler) Message(id string, raw []byte) error {
 
 	session, ok := h.sessions.Get(id)
 	if !ok {
-		errors.Errorf("unknown session id %s", id)
+		return errors.Errorf("unknown session id %s", id)
 	}
 
 	switch header.Event {