diff --git a/js/src/jsscript.cpp b/js/src/jsscript.cpp
index 0bef0187412c..e8c440e69c5f 100644
--- a/js/src/jsscript.cpp
+++ b/js/src/jsscript.cpp
@@ -357,6 +357,7 @@ js::XDRScript(XDRState<mode> *xdr, HandleObject enclosingScope, HandleScript enc
         OwnFilename,
         ParentFilename,
         IsGenerator,
+        IsGeneratorExp,
         HaveSource,
         OwnSource,
         ExplicitUseStrict
@@ -525,6 +526,8 @@ js::XDRScript(XDRState<mode> *xdr, HandleObject enclosingScope, HandleScript enc
         }
         if (script->isGenerator)
             scriptBits |= (1 << IsGenerator);
+        if (script->isGeneratorExp)
+            scriptBits |= (1 << IsGeneratorExp);
 
         JS_ASSERT(!script->compileAndGo);
         JS_ASSERT(!script->hasSingletons);
@@ -606,6 +609,8 @@ js::XDRScript(XDRState<mode> *xdr, HandleObject enclosingScope, HandleScript enc
             script->setNeedsArgsObj(true);
         if (scriptBits & (1 << IsGenerator))
             script->isGenerator = true;
+        if (scriptBits & (1 << IsGeneratorExp))
+            script->isGeneratorExp = true;
     }
 
     JS_STATIC_ASSERT(sizeof(jsbytecode) == 1);
@@ -1814,6 +1819,7 @@ JSScript::fullyInitFromEmitter(JSContext *cx, Handle<JSScript*> script, Bytecode
     if (bce->sc->inFunction()) {
         JS_ASSERT(!bce->script->noScriptRval);
         script->isGenerator = bce->sc->funIsGenerator();
+        script->isGeneratorExp = bce->sc->funbox() && bce->sc->funbox()->inGenexpLambda;
         script->setFunction(bce->sc->fun());
     }
 
@@ -2289,6 +2295,7 @@ js::CloneScript(JSContext *cx, HandleObject enclosingScope, HandleFunction fun,
     dst->funHasExtensibleScope = src->funHasExtensibleScope;
     dst->hasSingletons = src->hasSingletons;
     dst->isGenerator = src->isGenerator;
+    dst->isGeneratorExp = src->isGeneratorExp;
 
     /*
      * initScriptCounts updates scriptCountsMap if necessary. The other script
diff --git a/js/src/jsscript.h b/js/src/jsscript.h
index c58447cc87b7..5e832cd3f612 100644
--- a/js/src/jsscript.h
+++ b/js/src/jsscript.h
@@ -540,6 +540,7 @@ struct JSScript : public js::gc::Cell
 #endif
     bool            callDestroyHook:1;/* need to call destroy hook */
     bool            isGenerator:1;    /* is a generator */
+    bool            isGeneratorExp:1; /* is a generator expression */
     bool            hasScriptCounts:1;/* script has an entry in
                                          JSCompartment::scriptCountsMap */
     bool            hasSourceMap:1;   /* script has an entry in
diff --git a/js/src/vm/Xdr.h b/js/src/vm/Xdr.h
index 20dcf623b5ed..4514bdeb6112 100644
--- a/js/src/vm/Xdr.h
+++ b/js/src/vm/Xdr.h
@@ -25,7 +25,7 @@ namespace js {
  * and saved versions. If deserialization fails, the data should be
  * invalidated if possible.
  */
-static const uint32_t XDR_BYTECODE_VERSION = uint32_t(0xb973c0de - 123);
+static const uint32_t XDR_BYTECODE_VERSION = uint32_t(0xb973c0de - 124);
 
 class XDRBuffer {
   public: