diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index fb78aae2a..520205a91 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -1389,6 +1389,7 @@ pref("network.protocol-handler.external.vbscript", false);
 pref("network.protocol-handler.external.javascript", false);
 pref("network.protocol-handler.external.data", false);
 pref("network.protocol-handler.external.ms-help", false);
+pref("network.protocol-handler.external.res", false);
 pref("network.protocol-handler.external.shell", false);
 pref("network.protocol-handler.external.vnd.ms.radio", false);
 #ifdef XP_MACOSX