--- a/js/xpconnect/loader/mozJSComponentLoader.cpp
+++ b/js/xpconnect/loader/mozJSComponentLoader.cpp
@@ -646,16 +646,17 @@ mozJSComponentLoader::ObjectForLocation(
         // startup cache regresses installer size (due to source code stored in
         // 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_DEFAULT)
+               .maybeMakeStrictMode(true)
                .setFileAndLine(nativePath.get(), 1)
                .setSourceIsLazy(cache || ScriptPreloader::GetSingleton().Active());
 
         if (realFile) {
             AutoMemMap map;
             MOZ_TRY(map.init(aComponentFile));
 
             // Note: exceptions will get handled further down;