diff --git a/js/xpconnect/src/XPCJSRuntime.cpp b/js/xpconnect/src/XPCJSRuntime.cpp
index fa1d9724483..2786a833c15 100644
--- a/js/xpconnect/src/XPCJSRuntime.cpp
+++ b/js/xpconnect/src/XPCJSRuntime.cpp
@@ -2948,7 +2948,7 @@ XPCJSRuntime::XPCJSRuntime(nsXPConnect* aXPConnect)
    mVariantRoots(nullptr),
    mWrappedJSRoots(nullptr),
    mObjectHolderRoots(nullptr),
-   mWatchdogManager(new WatchdogManager(this)),
+   mWatchdogManager(new WatchdogManager(MOZ_THIS_IN_INITIALIZER_LIST())),
    mJunkScope(nullptr),
    mAsyncSnowWhiteFreer(new AsyncFreeSnowWhite())
 {
diff --git a/js/xpconnect/src/XPCWrappedJS.cpp b/js/xpconnect/src/XPCWrappedJS.cpp
index 78ad238c04f..f97b28c84ca 100644
--- a/js/xpconnect/src/XPCWrappedJS.cpp
+++ b/js/xpconnect/src/XPCWrappedJS.cpp
@@ -339,7 +339,7 @@ nsXPCWrappedJS::nsXPCWrappedJS(JSContext* cx,
                                nsISupports* aOuter)
     : mJSObj(aJSObj),
       mClass(aClass),
-      mRoot(root ? root : this),
+      mRoot(root ? root : MOZ_THIS_IN_INITIALIZER_LIST()),
       mNext(nullptr),
       mOuter(root ? nullptr : aOuter)
 {
diff --git a/js/xpconnect/src/xpcprivate.h b/js/xpconnect/src/xpcprivate.h
index 026e5599557..9957ae9659c 100644
--- a/js/xpconnect/src/xpcprivate.h
+++ b/js/xpconnect/src/xpcprivate.h
@@ -248,11 +248,6 @@ inline JSObject* GetWNExpandoChain(JSObject *obj)
     return JS_GetReservedSlot(obj, WN_XRAYEXPANDOCHAIN_SLOT).toObjectOrNull();
 }
 
-// We PROMISE to never screw this up.
-#ifdef _MSC_VER
-#pragma warning(disable : 4355) // OK to pass "this" in member initializer
-#endif
-
 /***************************************************************************
 ****************************************************************************
 *