diff --git a/js/src/builtin/RegExp.cpp b/js/src/builtin/RegExp.cpp
index 54bbc06e3ab6..0f8412421d34 100644
--- a/js/src/builtin/RegExp.cpp
+++ b/js/src/builtin/RegExp.cpp
@@ -230,7 +230,7 @@ CompileRegExpObject(JSContext *cx, RegExpObjectBuilder &builder, CallArgs args)
     }
 
     Value sourceValue = args[0];
-    if (ValueIsRegExp(sourceValue)) {
+    if (IsObjectWithClass(sourceValue, ESClass_RegExp, cx)) {
         /*
          * If we get passed in a |RegExpObject| source we return a new
          * object with the same source/flags.
@@ -243,9 +243,15 @@ CompileRegExpObject(JSContext *cx, RegExpObjectBuilder &builder, CallArgs args)
             return false;
         }
 
-        RegExpObject *reobj = builder.build(&sourceObj.asRegExp());
+        RegExpShared *shared = RegExpToShared(cx, sourceObj);
+        if (!shared)
+            return false;
+
+        shared->incref(cx);
+        RegExpObject *reobj = builder.build(AlreadyIncRefed<RegExpShared>(shared));
         if (!reobj)
             return false;
+
         args.rval() = ObjectValue(*reobj);
         return true;
     }
@@ -314,7 +320,7 @@ regexp_construct(JSContext *cx, uintN argc, Value *vp)
          * Otherwise, delegate to the standard constructor.
          * See ECMAv5 15.10.3.1.
          */
-        if (args.length() >= 1 && ValueIsRegExp(args[0]) &&
+        if (args.length() >= 1 && IsObjectWithClass(args[0], ESClass_RegExp, cx) &&
             (args.length() == 1 || args[1].isUndefined()))
         {
             args.rval() = args[0];
diff --git a/js/src/frontend/BytecodeEmitter.cpp b/js/src/frontend/BytecodeEmitter.cpp
index bdd171ee1a9b..367fea8ca5e0 100644
--- a/js/src/frontend/BytecodeEmitter.cpp
+++ b/js/src/frontend/BytecodeEmitter.cpp
@@ -983,7 +983,7 @@ static bool
 EmitIndex32(JSContext *cx, JSOp op, uint32_t index, BytecodeEmitter *bce)
 {
     const size_t len = 1 + UINT32_INDEX_LEN;
-    JS_ASSERT(js_CodeSpec[op].length == len);
+    JS_ASSERT(size_t(js_CodeSpec[op].length) == len);
     ptrdiff_t offset = EmitCheck(cx, bce, len);
     if (offset < 0)
         return false;
diff --git a/js/src/jit-test/tests/basic/testCrossCompartmentTransparency.js b/js/src/jit-test/tests/basic/testCrossCompartmentTransparency.js
index c93b704eee1a..d9d15d24a215 100644
--- a/js/src/jit-test/tests/basic/testCrossCompartmentTransparency.js
+++ b/js/src/jit-test/tests/basic/testCrossCompartmentTransparency.js
@@ -27,7 +27,6 @@ function test(str, f) {
         f(g1.eval("new Object()"));
     } catch (e) {
         assertEq(Object.prototype.toString.call(e), "[object Error]");
-        assertEq(e.name, "TypeError");
         threw = true;
     }
     assertEq(threw, true);
@@ -36,7 +35,6 @@ function test(str, f) {
         f(g2.eval("new Object()"));
     } catch (e) {
         assertEq(Object.prototype.toString.call(e), "[object Error]");
-        assertEq(e.name, "TypeError");
         threw = true;
     }
     assertEq(threw, true);
@@ -45,7 +43,6 @@ function test(str, f) {
         f(proxy1);
     } catch (e) {
         assertEq(Object.prototype.toString.call(e), "[object Error]");
-        assertEq(e.name, "TypeError");
         threw = true;
     }
     assertEq(threw, true);
@@ -54,7 +51,6 @@ function test(str, f) {
         f(proxy2);
     } catch (e) {
         assertEq(Object.prototype.toString.call(e), "[object Error]");
-        assertEq(e.name, "TypeError");
         threw = true;
     }
     assertEq(threw, true);
@@ -78,6 +74,13 @@ test("new RegExp('1')", function(r) RegExp.prototype.toString.call(r));
 test("new RegExp('1')", function(r) RegExp.prototype.exec.call(r, '1').toString());
 test("new RegExp('1')", function(r) RegExp.prototype.test.call(r, '1'));
 test("new RegExp('1')", function(r) RegExp.prototype.compile.call(r, '1').toString());
+test("new RegExp('1')", function(r) assertEq("a1".search(r), 1));
+test("new RegExp('1')", function(r) assertEq("a1".match(r)[0], '1'));
+test("new RegExp('1')", function(r) assertEq("a1".replace(r, 'A'), 'aA'));
+test("new RegExp('1')", function(r) assertEq(String("a1b".split(r)), "a,b"));
+test("new RegExp('1')", function(r) assertEq(r, RegExp(r)));
+test("new RegExp('1')", function(r) assertEq(String(new RegExp(r)), String(r)));
+test("new RegExp('1')", function(r) assertEq(String(/x/.compile(r)), String(r)));
 test("new WeakMap()", function(w) WeakMap.prototype.has.call(w, {}));
 test("new WeakMap()", function(w) WeakMap.prototype.get.call(w, {}));
 test("new WeakMap()", function(w) WeakMap.prototype.delete.call(w, {}));
diff --git a/js/src/jsarray.cpp b/js/src/jsarray.cpp
index d925a3b0e118..b32edd5e031f 100644
--- a/js/src/jsarray.cpp
+++ b/js/src/jsarray.cpp
@@ -3567,9 +3567,7 @@ static JSBool
 array_isArray(JSContext *cx, uintN argc, Value *vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
-    bool isArray = args.length() > 0 &&
-                   args[0].isObject() &&
-                   ObjectClassIs(args[0].toObject(), ESClass_Array, cx);
+    bool isArray = args.length() > 0 && IsObjectWithClass(args[0], ESClass_Array, cx);
     args.rval().setBoolean(isArray);
     return true;
 }
diff --git a/js/src/jsclass.h b/js/src/jsclass.h
index 5a3a18e578fa..37f911471df7 100644
--- a/js/src/jsclass.h
+++ b/js/src/jsclass.h
@@ -407,7 +407,9 @@ Valueify(const JSClass *c)
  * Enumeration describing possible values of the [[Class]] internal property
  * value of objects.
  */
-enum ESClassValue { ESClass_Array, ESClass_Number, ESClass_String, ESClass_Boolean };
+enum ESClassValue {
+    ESClass_Array, ESClass_Number, ESClass_String, ESClass_Boolean, ESClass_RegExp
+};
 
 /*
  * Return whether the given object has the given [[Class]] internal property
@@ -418,6 +420,10 @@ enum ESClassValue { ESClass_Array, ESClass_Number, ESClass_String, ESClass_Boole
 inline bool
 ObjectClassIs(JSObject &obj, ESClassValue classValue, JSContext *cx);
 
+/* Just a helper that checks v.isObject before calling ObjectClassIs. */
+inline bool
+IsObjectWithClass(const Value &v, ESClassValue classValue, JSContext *cx);
+
 }  /* namespace js */
 
 #endif  /* __cplusplus */
diff --git a/js/src/jsobjinlines.h b/js/src/jsobjinlines.h
index b80aada2aee4..9ba7180064a0 100644
--- a/js/src/jsobjinlines.h
+++ b/js/src/jsobjinlines.h
@@ -1953,11 +1953,20 @@ ObjectClassIs(JSObject &obj, ESClassValue classValue, JSContext *cx)
       case ESClass_Number: return obj.isNumber();
       case ESClass_String: return obj.isString();
       case ESClass_Boolean: return obj.isBoolean();
+      case ESClass_RegExp: return obj.isRegExp();
     }
     JS_NOT_REACHED("bad classValue");
     return false;
 }
 
+inline bool
+IsObjectWithClass(const Value &v, ESClassValue classValue, JSContext *cx)
+{
+    if (!v.isObject())
+        return false;
+    return ObjectClassIs(v.toObject(), classValue, cx);
+}
+
 static JS_ALWAYS_INLINE bool
 ValueIsSpecial(JSObject *obj, Value *propval, SpecialId *sidp, JSContext *cx)
 {
diff --git a/js/src/jsproxy.cpp b/js/src/jsproxy.cpp
index 5b5693655a8e..f5024caf63ec 100644
--- a/js/src/jsproxy.cpp
+++ b/js/src/jsproxy.cpp
@@ -301,6 +301,13 @@ ProxyHandler::fun_toString(JSContext *cx, JSObject *proxy, uintN indent)
     return fun_toStringHelper(cx, &fval.toObject(), indent);
 }
 
+RegExpShared *
+ProxyHandler::regexp_toShared(JSContext *cx, JSObject *proxy)
+{
+    JS_NOT_REACHED("This should have been a wrapped regexp");
+    return (RegExpShared *)NULL;
+}
+
 bool
 ProxyHandler::defaultValue(JSContext *cx, JSObject *proxy, JSType hint, Value *vp)
 {
@@ -946,6 +953,14 @@ Proxy::fun_toString(JSContext *cx, JSObject *proxy, uintN indent)
     return GetProxyHandler(proxy)->fun_toString(cx, proxy, indent);
 }
 
+RegExpShared *
+Proxy::regexp_toShared(JSContext *cx, JSObject *proxy)
+{
+    JS_CHECK_RECURSION(cx, return NULL);
+    AutoPendingProxyOperation pending(cx, proxy);
+    return GetProxyHandler(proxy)->regexp_toShared(cx, proxy);
+}
+
 bool
 Proxy::defaultValue(JSContext *cx, JSObject *proxy, JSType hint, Value *vp)
 {
diff --git a/js/src/jsproxy.h b/js/src/jsproxy.h
index 3377f98247ec..fb21c9e1ad9c 100644
--- a/js/src/jsproxy.h
+++ b/js/src/jsproxy.h
@@ -84,6 +84,7 @@ class JS_FRIEND_API(ProxyHandler) {
     virtual bool objectClassIs(JSObject *obj, ESClassValue classValue, JSContext *cx);
     virtual JSString *obj_toString(JSContext *cx, JSObject *proxy);
     virtual JSString *fun_toString(JSContext *cx, JSObject *proxy, uintN indent);
+    virtual RegExpShared *regexp_toShared(JSContext *cx, JSObject *proxy);
     virtual bool defaultValue(JSContext *cx, JSObject *obj, JSType hint, Value *vp);
     virtual void finalize(JSContext *cx, JSObject *proxy);
     virtual void trace(JSTracer *trc, JSObject *proxy);
@@ -137,6 +138,7 @@ class Proxy {
     static bool objectClassIs(JSObject *obj, ESClassValue classValue, JSContext *cx);
     static JSString *obj_toString(JSContext *cx, JSObject *proxy);
     static JSString *fun_toString(JSContext *cx, JSObject *proxy, uintN indent);
+    static RegExpShared *regexp_toShared(JSContext *cx, JSObject *proxy);
     static bool defaultValue(JSContext *cx, JSObject *obj, JSType hint, Value *vp);
 };
 
diff --git a/js/src/jsstr.cpp b/js/src/jsstr.cpp
index e99866afa9bf..56fcece72d73 100644
--- a/js/src/jsstr.cpp
+++ b/js/src/jsstr.cpp
@@ -1400,11 +1400,11 @@ class RegExpGuard
     bool
     init(CallArgs args, bool convertVoid = false)
     {
-        if (args.length() != 0 && ValueIsRegExp(args[0])) {
-            RegExpObject &reobj = args[0].toObject().asRegExp();
-            RegExpShared *shared = reobj.getShared(cx);
+        if (args.length() != 0 && IsObjectWithClass(args[0], ESClass_RegExp, cx)) {
+            RegExpShared *shared = RegExpToShared(cx, args[0].toObject());
             if (!shared)
                 return false;
+
             matcher.init(NeedsIncRef<RegExpShared>(shared));
         } else {
             if (convertVoid && (args.length() == 0 || args[0].isUndefined())) {
@@ -2547,9 +2547,8 @@ js::str_split(JSContext *cx, uintN argc, Value *vp)
     JSLinearString *sepstr = NULL;
     bool sepUndefined = (args.length() == 0 || args[0].isUndefined());
     if (!sepUndefined) {
-        if (ValueIsRegExp(args[0])) {
-            RegExpObject &reobj = args[0].toObject().asRegExp();
-            RegExpShared *shared = reobj.getShared(cx);
+        if (IsObjectWithClass(args[0], ESClass_RegExp, cx)) {
+            RegExpShared *shared = RegExpToShared(cx, args[0].toObject());
             if (!shared)
                 return false;
             matcher.init(NeedsIncRef<RegExpShared>(shared));
diff --git a/js/src/jswrapper.cpp b/js/src/jswrapper.cpp
index 5d2c7156eb30..254a2ab214c7 100644
--- a/js/src/jswrapper.cpp
+++ b/js/src/jswrapper.cpp
@@ -54,10 +54,10 @@
 #endif
 #include "jscompartment.h"
 
-#include "vm/RegExpObject.h"
-
 #include "jsobjinlines.h"
 
+#include "vm/RegExpObject-inl.h"
+
 using namespace js;
 using namespace js::gc;
 
@@ -334,6 +334,12 @@ Wrapper::fun_toString(JSContext *cx, JSObject *wrapper, uintN indent)
     return str;
 }
 
+RegExpShared *
+Wrapper::regexp_toShared(JSContext *cx, JSObject *wrapper)
+{
+    return wrappedObject(wrapper)->asRegExp().getShared(cx);
+}
+
 bool
 Wrapper::defaultValue(JSContext *cx, JSObject *wrapper, JSType hint, Value *vp)
 {
@@ -881,5 +887,13 @@ SecurityWrapper<Base>::objectClassIs(JSObject *obj, ESClassValue classValue, JSC
     return Base::objectClassIs(obj, classValue, cx);
 }
 
+template <class Base>
+RegExpShared *
+SecurityWrapper<Base>::regexp_toShared(JSContext *cx, JSObject *obj)
+{
+    return Base::regexp_toShared(cx, obj);
+}
+
+
 template class js::SecurityWrapper<Wrapper>;
 template class js::SecurityWrapper<CrossCompartmentWrapper>;
diff --git a/js/src/jswrapper.h b/js/src/jswrapper.h
index e9ddd8fc7011..8edf4e4f3830 100644
--- a/js/src/jswrapper.h
+++ b/js/src/jswrapper.h
@@ -94,6 +94,7 @@ class JS_FRIEND_API(Wrapper) : public ProxyHandler
     virtual bool objectClassIs(JSObject *obj, ESClassValue classValue, JSContext *cx) MOZ_OVERRIDE;
     virtual JSString *obj_toString(JSContext *cx, JSObject *wrapper) MOZ_OVERRIDE;
     virtual JSString *fun_toString(JSContext *cx, JSObject *wrapper, uintN indent) MOZ_OVERRIDE;
+    virtual RegExpShared *regexp_toShared(JSContext *cx, JSObject *proxy) MOZ_OVERRIDE;
     virtual bool defaultValue(JSContext *cx, JSObject *wrapper, JSType hint, Value *vp) MOZ_OVERRIDE;
 
     virtual void trace(JSTracer *trc, JSObject *wrapper) MOZ_OVERRIDE;
@@ -178,6 +179,7 @@ class JS_FRIEND_API(SecurityWrapper) : public Base
 
     virtual bool nativeCall(JSContext *cx, JSObject *wrapper, Class *clasp, Native native, CallArgs args) MOZ_OVERRIDE;
     virtual bool objectClassIs(JSObject *obj, ESClassValue classValue, JSContext *cx) MOZ_OVERRIDE;
+    virtual RegExpShared *regexp_toShared(JSContext *cx, JSObject *proxy) MOZ_OVERRIDE;
 };
 
 typedef SecurityWrapper<Wrapper> SameCompartmentSecurityWrapper;
diff --git a/js/src/vm/RegExpObject-inl.h b/js/src/vm/RegExpObject-inl.h
index 4d2a45e5e313..4f060d418d4c 100644
--- a/js/src/vm/RegExpObject-inl.h
+++ b/js/src/vm/RegExpObject-inl.h
@@ -59,12 +59,6 @@ JSObject::asRegExp()
 
 namespace js {
 
-inline bool
-ValueIsRegExp(const Value &v)
-{
-    return !v.isPrimitive() && v.toObject().isRegExp();
-}
-
 inline bool
 IsRegExpMetaChar(jschar c)
 {
@@ -506,6 +500,15 @@ RegExpShared::decref(JSContext *cx)
 #endif
 }
 
+inline RegExpShared *
+RegExpToShared(JSContext *cx, JSObject &obj)
+{
+    JS_ASSERT(ObjectClassIs(obj, ESClass_RegExp, cx));
+    if (obj.isRegExp())
+        return obj.asRegExp().getShared(cx);
+    return Proxy::regexp_toShared(cx, &obj);
+}
+
 } /* namespace js */
 
 #endif
diff --git a/js/src/vm/RegExpObject.cpp b/js/src/vm/RegExpObject.cpp
index 113fb800fc66..d72865062d90 100644
--- a/js/src/vm/RegExpObject.cpp
+++ b/js/src/vm/RegExpObject.cpp
@@ -137,18 +137,6 @@ RegExpObjectBuilder::build(JSLinearString *source, RegExpFlag flags)
     return reobj_->init(cx, source, flags) ? reobj_ : NULL;
 }
 
-RegExpObject *
-RegExpObjectBuilder::build(RegExpObject *other)
-{
-    RegExpShared *shared = other->getShared(cx);
-    if (!shared)
-        return NULL;
-
-    /* Now, incref it for the RegExpObject being built. */
-    shared->incref(cx);
-    return build(AlreadyIncRefed<RegExpShared>(shared));
-}
-
 RegExpObject *
 RegExpObjectBuilder::clone(RegExpObject *other, RegExpObject *proto)
 {
diff --git a/js/src/vm/RegExpObject.h b/js/src/vm/RegExpObject.h
index f039f2bb42e1..12931131fe74 100644
--- a/js/src/vm/RegExpObject.h
+++ b/js/src/vm/RegExpObject.h
@@ -207,8 +207,6 @@ class RegExpObjectBuilder
     bool getOrCreate();
     bool getOrCreateClone(RegExpObject *proto);
 
-    RegExpObject *build(AlreadyIncRefed<RegExpShared> shared);
-
     friend class RegExpMatcher;
 
   public:
@@ -219,7 +217,7 @@ class RegExpObjectBuilder
     RegExpObject *reobj() { return reobj_; }
 
     RegExpObject *build(JSLinearString *str, RegExpFlag flags);
-    RegExpObject *build(RegExpObject *other);
+    RegExpObject *build(AlreadyIncRefed<RegExpShared> shared);
 
     /* Perform a VM-internal clone. */
     RegExpObject *clone(RegExpObject *other, RegExpObject *proto);
@@ -469,9 +467,6 @@ class RegExpMatcher
 bool
 ParseRegExpFlags(JSContext *cx, JSString *flagStr, RegExpFlag *flagsOut);
 
-inline bool
-ValueIsRegExp(const Value &v);
-
 inline bool
 IsRegExpMetaChar(jschar c);
 
@@ -481,6 +476,9 @@ CheckRegExpSyntax(JSContext *cx, JSLinearString *str)
     return detail::RegExpCode::checkSyntax(cx, NULL, str);
 }
 
+inline RegExpShared *
+RegExpToShared(JSContext *cx, JSObject &obj);
+
 } /* namespace js */
 
 extern JS_FRIEND_API(JSObject *) JS_FASTCALL