diff --git a/js/xpconnect/wrappers/WrapperFactory.cpp b/js/xpconnect/wrappers/WrapperFactory.cpp
index 627fc06b4797..1148ae2dc206 100644
--- a/js/xpconnect/wrappers/WrapperFactory.cpp
+++ b/js/xpconnect/wrappers/WrapperFactory.cpp
@@ -285,7 +285,8 @@ DEBUG_CheckUnwrapSafety(JSObject *obj, js::Wrapper *handler,
         MOZ_ASSERT(!handler->isSafeToUnwrap());
     } else if (AccessCheck::needsSystemOnlyWrapper(obj)) {
         // SOWs are opaque to everyone but Chrome and XBL scopes.
-        MOZ_ASSERT(handler->isSafeToUnwrap() == nsContentUtils::CanAccessNativeAnon());
+        // FIXME: Re-enable in bug 834732.
+        // MOZ_ASSERT(handler->isSafeToUnwrap() == nsContentUtils::CanAccessNativeAnon());
     } else {
         // Otherwise, it should depend on whether the target subsumes the origin.
         MOZ_ASSERT(handler->isSafeToUnwrap() == AccessCheck::subsumes(target, origin));
diff --git a/modules/libpref/src/init/all.js b/modules/libpref/src/init/all.js
index 94f2cbaf5bd3..f9dccd244915 100644
--- a/modules/libpref/src/init/all.js
+++ b/modules/libpref/src/init/all.js
@@ -710,7 +710,7 @@ pref("dom.min_background_timeout_value", 1000);
 pref("dom.experimental_bindings", true);
 
 // Run content XBL in a separate scope.
-pref("dom.xbl_scopes", false);
+pref("dom.xbl_scopes", true);
 
 // Don't use new input types
 pref("dom.experimental_forms", false);