--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -1388,17 +1388,21 @@ pref("dom.event.clipboardevents.enabled"
 pref("dom.event.highrestimestamp.enabled",  true);
 #ifdef NIGHTLY_BUILD
 pref("dom.event.coalesce_mouse_move",       true);
 #else
 pref("dom.event.coalesce_mouse_move",       false);
 #endif
 
 pref("dom.webcomponents.enabled",           false);
+#ifdef NIGHTLY_BUILD
+pref("dom.webcomponents.customelements.enabled", true);
+#else
 pref("dom.webcomponents.customelements.enabled", false);
+#endif
 
 pref("javascript.enabled",                  true);
 pref("javascript.options.strict",           false);
 #ifdef DEBUG
 pref("javascript.options.strict.debug",     false);
 #endif
 pref("javascript.options.baselinejit",      true);
 pref("javascript.options.ion",              true);