diff --git a/js/xpconnect/loader/ChromeScriptLoader.cpp b/js/xpconnect/loader/ChromeScriptLoader.cpp
index 109e3af196f4..315b45211b7a 100644
--- a/js/xpconnect/loader/ChromeScriptLoader.cpp
+++ b/js/xpconnect/loader/ChromeScriptLoader.cpp
@@ -49,6 +49,8 @@ public:
       , mGlobalObject(aGlobal)
       , mPromise(aPromise)
       , mCharset(aOptions.mCharset)
+      , mToken(nullptr)
+      , mScriptLength(0)
     {
         mOptions.setNoScriptRval(!aOptions.mHasReturnValue)
                 .setCanLazilyParse(aOptions.mLazilyParse)
diff --git a/js/xpconnect/src/BackstagePass.h b/js/xpconnect/src/BackstagePass.h
index be7d15cdff1d..13ec166f4b25 100644
--- a/js/xpconnect/src/BackstagePass.h
+++ b/js/xpconnect/src/BackstagePass.h
@@ -41,7 +41,7 @@ public:
   void SetGlobalObject(JSObject* global);
 
   explicit BackstagePass(nsIPrincipal* prin) :
-    mPrincipal(prin)
+    mPrincipal(prin), mWrapper(nullptr)
   {
   }
 
diff --git a/js/xpconnect/src/XPCCallContext.cpp b/js/xpconnect/src/XPCCallContext.cpp
index 67081e2dfc1d..7914db051be4 100644
--- a/js/xpconnect/src/XPCCallContext.cpp
+++ b/js/xpconnect/src/XPCCallContext.cpp
@@ -34,7 +34,12 @@ XPCCallContext::XPCCallContext(JSContext* cx,
         mJSContext(cx),
         mWrapper(nullptr),
         mTearOff(nullptr),
-        mName(cx)
+        mMember(nullptr),
+        mName(cx),
+        mStaticMemberIsLocal(false),
+        mArgc(0),
+        mArgv(nullptr),
+        mRetVal(nullptr)
 {
     MOZ_ASSERT(cx);
     MOZ_ASSERT(cx == nsContentUtils::GetCurrentJSContext());
diff --git a/js/xpconnect/src/xpcprivate.h b/js/xpconnect/src/xpcprivate.h
index 1e569afa5113..71ff7be750d8 100644
--- a/js/xpconnect/src/xpcprivate.h
+++ b/js/xpconnect/src/xpcprivate.h
@@ -295,10 +295,8 @@ class XPCRootSetElem
 public:
     XPCRootSetElem()
     {
-#ifdef DEBUG
         mNext = nullptr;
         mSelfp = nullptr;
-#endif
     }
 
     ~XPCRootSetElem()