--- a/js/xpconnect/loader/ScriptPreloader.cpp
+++ b/js/xpconnect/loader/ScriptPreloader.cpp
@@ -691,17 +691,17 @@ ScriptPreloader::Run()
 }
 
 void
 ScriptPreloader::NoteScript(const nsCString& url, const nsCString& cachePath,
                             JS::HandleScript jsscript)
 {
     // Don't bother trying to cache any URLs with cache-busting query
     // parameters.
-    if (mStartupFinished || !mCacheInitialized || cachePath.FindChar('?') >= 0) {
+    if (!Active() || cachePath.FindChar('?') >= 0) {
         return;
     }
 
     // Don't bother caching files that belong to the mochitest harness.
     NS_NAMED_LITERAL_CSTRING(mochikitPrefix, "chrome://mochikit/");
     if (StringHead(url, mochikitPrefix.Length()) == mochikitPrefix) {
         return;
     }
@@ -935,17 +935,18 @@ ScriptPreloader::DecodeNextBatch(size_t 
         return;
     }
 
     AutoJSAPI jsapi;
     MOZ_RELEASE_ASSERT(jsapi.Init(xpc::CompilationScope()));
     JSContext* cx = jsapi.cx();
 
     JS::CompileOptions options(cx, JSVERSION_LATEST);
-    options.setNoScriptRval(true);
+    options.setNoScriptRval(true)
+           .setSourceIsLazy(true);
 
     if (!JS::CanCompileOffThread(cx, options, size) ||
         !JS::DecodeMultiOffThreadScripts(cx, options, mParsingSources,
                                          OffThreadDecodeCallback,
                                          static_cast<void*>(this))) {
         // If we fail here, we don't move on to process the next batch, so make
         // sure we don't have any other scripts left to process.
         MOZ_ASSERT(mPendingScripts.isEmpty());

--- a/js/xpconnect/loader/ScriptPreloader.h
+++ b/js/xpconnect/loader/ScriptPreloader.h
@@ -86,16 +86,21 @@ public:
                     ProcessType processType, nsTArray<uint8_t>&& xdrData,
                     TimeStamp loadTime);
 
     // Initializes the script cache from the startup script cache file.
     Result<Ok, nsresult> InitCache(const nsAString& = NS_LITERAL_STRING("scriptCache"));
 
     Result<Ok, nsresult> InitCache(const Maybe<ipc::FileDescriptor>& cacheFile, ScriptCacheChild* cacheChild);
 
+    bool Active()
+    {
+      return mCacheInitialized && !mStartupFinished;
+    }
+
 private:
     Result<Ok, nsresult> InitCacheInternal();
 
 public:
     void Trace(JSTracer* trc);
 
     static ProcessType CurrentProcessType()
     {

--- a/js/xpconnect/loader/mozJSComponentLoader.cpp
+++ b/js/xpconnect/loader/mozJSComponentLoader.cpp
@@ -642,17 +642,17 @@ mozJSComponentLoader::ObjectForLocation(
         // XDR encoded modules in omni.ja). Also, XDR decoding is relatively
         // fast. When we're not using the startup cache, we want to use non-lazy
         // source code so that we can use lazy parsing.
         // See bug 1303754.
         CompileOptions options(cx);
         options.setNoScriptRval(true)
                .setVersion(JSVERSION_LATEST)
                .setFileAndLine(nativePath.get(), 1)
-               .setSourceIsLazy(!!cache);
+               .setSourceIsLazy(cache || ScriptPreloader::GetSingleton().Active());
 
         if (realFile) {
             AutoMemMap map;
             MOZ_TRY(map.init(aComponentFile));
 
             // Note: exceptions will get handled further down;
             // don't early return for them here.
             auto buf = map.get<char>();