diff --git a/win/vncviewer/CConn.cxx b/win/vncviewer/CConn.cxx
index 74d6818..1f4bbc2 100644
--- a/win/vncviewer/CConn.cxx
+++ b/win/vncviewer/CConn.cxx
@@ -436,7 +436,7 @@
 void
 CConn::bell() {
   if (options.acceptBell)
-    MessageBeep(-1);
+    MessageBeep((UINT)-1);
 }