diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index 466fc2d4a014..dc8b43dde5d3 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -126,25 +126,25 @@ JS::detail::CallMethodIfWrapped(JSContext *cx, IsAcceptableThis test, NativeImpl
 /*
  * This class is a version-establishing barrier at the head of a VM entry or
  * re-entry. It ensures that |newVersion| is the starting (default) version
- * used for the context.
+ * used for the runtime.
  */
 class AutoVersionAPI
 {
-    JSContext   * const cx;
+    JSRuntime   * const rt;
     JSVersion   oldDefaultVersion;
     JSVersion   newVersion;
 
   public:
-    AutoVersionAPI(JSContext *cx, JSVersion newVersion)
-      : cx(cx),
-        oldDefaultVersion(cx->getDefaultVersion())
+    AutoVersionAPI(JSRuntime *rt, JSVersion newVersion)
+      : rt(rt),
+        oldDefaultVersion(rt->defaultVersion())
     {
         this->newVersion = newVersion;
-        cx->setDefaultVersion(newVersion);
+        rt->setDefaultVersion(newVersion);
     }
 
     ~AutoVersionAPI() {
-        cx->setDefaultVersion(oldDefaultVersion);
+        rt->setDefaultVersion(oldDefaultVersion);
     }
 
     /* The version that this scoped-entity establishes. */
@@ -740,6 +740,7 @@ JSRuntime::JSRuntime(JSUseHelperThreads useHelperThreads)
     numCompartments(0),
     localeCallbacks(NULL),
     defaultLocale(NULL),
+    defaultVersion_(JSVERSION_DEFAULT),
 #ifdef JS_THREADSAFE
     ownerThread_(NULL),
 #endif
@@ -5173,7 +5174,7 @@ JS::Compile(JSContext *cx, HandleObject obj, CompileOptions options,
 {
     Maybe<AutoVersionAPI> mava;
     if (options.versionSet) {
-        mava.construct(cx, options.version);
+        mava.construct(cx->runtime(), options.version);
         // AutoVersionAPI propagates some compilation flags through.
         options.version = mava.ref().version();
     }
@@ -5332,7 +5333,7 @@ JS::CompileFunction(JSContext *cx, HandleObject obj, CompileOptions options,
 {
     Maybe<AutoVersionAPI> mava;
     if (options.versionSet) {
-        mava.construct(cx, options.version);
+        mava.construct(cx->runtime(), options.version);
         // AutoVersionAPI propagates some compilation flags through.
         options.version = mava.ref().version();
     }
@@ -5512,7 +5513,7 @@ JS_ExecuteScriptVersion(JSContext *cx, JSObject *objArg, JSScript *script, jsval
                         JSVersion version)
 {
     RootedObject obj(cx, objArg);
-    AutoVersionAPI ava(cx, version);
+    AutoVersionAPI ava(cx->runtime(), version);
     return JS_ExecuteScript(cx, obj, script, rval);
 }
 
@@ -5524,7 +5525,7 @@ JS::Evaluate(JSContext *cx, HandleObject obj, CompileOptions options,
 {
     Maybe<AutoVersionAPI> mava;
     if (options.versionSet) {
-        mava.construct(cx, options.version);
+        mava.construct(cx->runtime(), options.version);
         // AutoVersionAPI propagates some compilation flags through.
         options.version = mava.ref().version();
     }
diff --git a/js/src/jscntxt.cpp b/js/src/jscntxt.cpp
index 4aeb66c19d7e..6f6b9d491eb0 100644
--- a/js/src/jscntxt.cpp
+++ b/js/src/jscntxt.cpp
@@ -296,8 +296,6 @@ js::NewContext(JSRuntime *rt, size_t stackChunkSize)
     if (!cx)
         return NULL;
 
-    JS_ASSERT(cx->findVersion() == JSVERSION_DEFAULT);
-
     if (!cx->cycleDetectorSet.init()) {
         js_delete(cx);
         return NULL;
@@ -1177,7 +1175,6 @@ ThreadSafeContext::asForkJoinSlice()
 
 JSContext::JSContext(JSRuntime *rt)
   : ThreadSafeContext(rt, &rt->mainThread, Context_JS),
-    defaultVersion(JSVERSION_DEFAULT),
     throwing(false),
     exception(UndefinedValue()),
     options_(0),
@@ -1535,7 +1532,7 @@ JSContext::findVersion() const
     if (compartment() && compartment()->options().hasVersion)
         return compartment()->options().version;
 
-    return defaultVersion;
+    return runtime()->defaultVersion();
 }
 
 #if defined JS_THREADSAFE && defined DEBUG
diff --git a/js/src/jscntxt.h b/js/src/jscntxt.h
index f4c5c9b0abe3..fd17d3b4d7a3 100644
--- a/js/src/jscntxt.h
+++ b/js/src/jscntxt.h
@@ -740,6 +740,9 @@ struct JSRuntime : public JS::shadow::Runtime,
     /* Default locale for Internationalization API */
     char *defaultLocale;
 
+    /* Default JSVersion. */
+    JSVersion defaultVersion_;
+
     /* See comment for JS_AbortIfWrongThread in jsapi.h. */
 #ifdef JS_THREADSAFE
   public:
@@ -852,6 +855,9 @@ struct JSRuntime : public JS::shadow::Runtime,
     /* Gets current default locale. String remains owned by context. */
     const char *getDefaultLocale();
 
+    JSVersion defaultVersion() { return defaultVersion_; }
+    void setDefaultVersion(JSVersion v) { defaultVersion_ = v; }
+
     /* Base address of the native stack for the current thread. */
     uintptr_t           nativeStackBase;
 
@@ -1655,9 +1661,6 @@ struct JSContext : js::ThreadSafeContext,
     js::PerThreadData &mainThread() const { return runtime()->mainThread; }
 
   private:
-    /* See JSContext::findVersion. */
-    JSVersion           defaultVersion;      /* script compilation version */
-
     /* Exception state -- the exception member is a GC root by definition. */
     bool                throwing;            /* is there a pending exception? */
     js::Value           exception;           /* most-recently-thrown exception */
@@ -1756,12 +1759,6 @@ struct JSContext : js::ThreadSafeContext,
     inline js::RegExpStatics *regExpStatics();
 
   public:
-    /* Set the default script compilation version. */
-    void setDefaultVersion(JSVersion version) {
-        defaultVersion = version;
-    }
-
-    JSVersion getDefaultVersion() const { return defaultVersion; }
 
     /*
      * Return: