diff --git a/dom/base/WindowNamedPropertiesHandler.h b/dom/base/WindowNamedPropertiesHandler.h
index cd0df01c36dc..a9570d2999ab 100644
--- a/dom/base/WindowNamedPropertiesHandler.h
+++ b/dom/base/WindowNamedPropertiesHandler.h
@@ -15,9 +15,9 @@ namespace dom {
 class WindowNamedPropertiesHandler : public BaseDOMProxyHandler
 {
 public:
-  WindowNamedPropertiesHandler()
-    : BaseDOMProxyHandler(nullptr, /* hasPrototype = */ true)
+  WindowNamedPropertiesHandler() : BaseDOMProxyHandler(nullptr)
   {
+    setHasPrototype(true);
   }
   virtual bool
   preventExtensions(JSContext* aCx, JS::Handle<JSObject*> aProxy) MOZ_OVERRIDE
diff --git a/dom/bindings/DOMJSProxyHandler.h b/dom/bindings/DOMJSProxyHandler.h
index d806b37ce347..d5a8bb4d2dc9 100644
--- a/dom/bindings/DOMJSProxyHandler.h
+++ b/dom/bindings/DOMJSProxyHandler.h
@@ -38,8 +38,8 @@ inline bool IsDOMProxy(JSObject *obj)
 class BaseDOMProxyHandler : public js::BaseProxyHandler
 {
 public:
-  BaseDOMProxyHandler(const void* aProxyFamily, bool aHasPrototype = false)
-    : js::BaseProxyHandler(aProxyFamily, aHasPrototype)
+  BaseDOMProxyHandler(const void* aProxyFamily)
+    : js::BaseProxyHandler(aProxyFamily)
   {}
 
   // Implementations of traps that can be implemented in terms of
diff --git a/js/src/jsproxy.cpp b/js/src/jsproxy.cpp
index 102cb6490618..a4718fffcc6e 100644
--- a/js/src/jsproxy.cpp
+++ b/js/src/jsproxy.cpp
@@ -79,10 +79,10 @@ js::assertEnteredPolicy(JSContext *cx, JSObject *proxy, jsid id,
 }
 #endif
 
-BaseProxyHandler::BaseProxyHandler(const void *family, bool hasPrototype, bool hasSecurityPolicy)
+BaseProxyHandler::BaseProxyHandler(const void *family)
   : mFamily(family),
-    mHasPrototype(hasPrototype),
-    mHasSecurityPolicy(hasSecurityPolicy)
+    mHasPrototype(false),
+    mHasSecurityPolicy(false)
 {
 }
 
@@ -538,9 +538,8 @@ DirectProxyHandler::weakmapKeyDelegate(JSObject *proxy)
     return UncheckedUnwrap(proxy);
 }
 
-DirectProxyHandler::DirectProxyHandler(const void *family, bool hasPrototype,
-                                       bool hasSecurityPolicy)
-  : BaseProxyHandler(family, hasPrototype, hasSecurityPolicy)
+DirectProxyHandler::DirectProxyHandler(const void *family)
+  : BaseProxyHandler(family)
 {
 }
 
diff --git a/js/src/jsproxy.h b/js/src/jsproxy.h
index eeaaf039e2db..aea22e60823f 100644
--- a/js/src/jsproxy.h
+++ b/js/src/jsproxy.h
@@ -116,9 +116,13 @@ class JS_FRIEND_API(BaseProxyHandler)
      */
     bool mHasSecurityPolicy;
 
+  protected:
+    // Subclasses may set this in their constructor.
+    void setHasPrototype(bool aHasPrototype) { mHasPrototype = aHasPrototype; }
+    void setHasSecurityPolicy(bool aHasPolicy) { mHasSecurityPolicy = aHasPolicy; }
+
   public:
-    explicit BaseProxyHandler(const void *family, bool hasPrototype = false,
-                              bool hasSecurityPolicy = false);
+    explicit BaseProxyHandler(const void *family);
     virtual ~BaseProxyHandler();
 
     bool hasPrototype() {
@@ -237,8 +241,7 @@ class JS_FRIEND_API(BaseProxyHandler)
 class JS_PUBLIC_API(DirectProxyHandler) : public BaseProxyHandler
 {
   public:
-    explicit DirectProxyHandler(const void *family, bool hasPrototype = false,
-                                bool hasSecurityPolicy = false);
+    explicit DirectProxyHandler(const void *family);
 
     /* ES5 Harmony fundamental proxy traps. */
     virtual bool preventExtensions(JSContext *cx, HandleObject proxy) MOZ_OVERRIDE;
diff --git a/js/src/jswrapper.cpp b/js/src/jswrapper.cpp
index b57c74e63c8d..ff5f9b4e8d10 100644
--- a/js/src/jswrapper.cpp
+++ b/js/src/jswrapper.cpp
@@ -127,10 +127,10 @@ js::IsCrossCompartmentWrapper(JSObject *obj)
            !!(Wrapper::wrapperHandler(obj)->flags() & Wrapper::CROSS_COMPARTMENT);
 }
 
-Wrapper::Wrapper(unsigned flags, bool hasPrototype, bool hasSecurityPolicy)
-  : DirectProxyHandler(&sWrapperFamily, hasPrototype, hasSecurityPolicy),
-    mFlags(flags)
+Wrapper::Wrapper(unsigned flags, bool hasPrototype) : DirectProxyHandler(&sWrapperFamily)
+                                                    , mFlags(flags)
 {
+    setHasPrototype(hasPrototype);
 }
 
 Wrapper::~Wrapper()
@@ -170,9 +170,8 @@ ErrorCopier::~ErrorCopier()
 
 /* Cross compartment wrappers. */
 
-CrossCompartmentWrapper::CrossCompartmentWrapper(unsigned flags, bool hasPrototype,
-                                                 bool hasSecurityPolicy)
-  : Wrapper(CROSS_COMPARTMENT | flags, hasPrototype, hasSecurityPolicy)
+CrossCompartmentWrapper::CrossCompartmentWrapper(unsigned flags, bool hasPrototype)
+  : Wrapper(CROSS_COMPARTMENT | flags, hasPrototype)
 {
 }
 
@@ -608,9 +607,10 @@ CrossCompartmentWrapper CrossCompartmentWrapper::singleton(0u);
 /* Security wrappers. */
 
 template <class Base>
-SecurityWrapper<Base>::SecurityWrapper(unsigned flags, bool hasPrototype)
-  : Base(flags, hasPrototype, /* hasSecurityPolicy = */ true)
+SecurityWrapper<Base>::SecurityWrapper(unsigned flags)
+  : Base(flags)
 {
+    BaseProxyHandler::setHasSecurityPolicy(true);
 }
 
 template <class Base>
diff --git a/js/src/jswrapper.h b/js/src/jswrapper.h
index 8311d8031585..a7561958bf42 100644
--- a/js/src/jswrapper.h
+++ b/js/src/jswrapper.h
@@ -81,7 +81,7 @@ class JS_FRIEND_API(Wrapper) : public DirectProxyHandler
         return mFlags;
     }
 
-    explicit Wrapper(unsigned flags, bool hasPrototype = false, bool hasSecurityPolicy = false);
+    explicit Wrapper(unsigned flags, bool hasPrototype = false);
 
     virtual ~Wrapper();
 
@@ -103,8 +103,7 @@ WrapperOptions::proto() const
 class JS_FRIEND_API(CrossCompartmentWrapper) : public Wrapper
 {
   public:
-    explicit CrossCompartmentWrapper(unsigned flags, bool hasPrototype = false,
-                                     bool hasSecurityPolicy = false);
+    explicit CrossCompartmentWrapper(unsigned flags, bool hasPrototype = false);
 
     virtual ~CrossCompartmentWrapper();
 
@@ -168,7 +167,7 @@ template <class Base>
 class JS_FRIEND_API(SecurityWrapper) : public Base
 {
   public:
-    explicit SecurityWrapper(unsigned flags, bool hasPrototype = false);
+    explicit SecurityWrapper(unsigned flags);
 
     virtual bool isExtensible(JSContext *cx, HandleObject wrapper, bool *extensible) MOZ_OVERRIDE;
     virtual bool preventExtensions(JSContext *cx, HandleObject wrapper) MOZ_OVERRIDE;
diff --git a/js/xpconnect/wrappers/XrayWrapper.cpp b/js/xpconnect/wrappers/XrayWrapper.cpp
index 1e31fcfb58f2..ef11332ac68c 100644
--- a/js/xpconnect/wrappers/XrayWrapper.cpp
+++ b/js/xpconnect/wrappers/XrayWrapper.cpp
@@ -1986,8 +1986,9 @@ DOMXrayTraits::createHolder(JSContext *cx, JSObject *wrapper)
 
 template <typename Base, typename Traits>
 XrayWrapper<Base, Traits>::XrayWrapper(unsigned flags)
-  : Base(flags | WrapperFactory::IS_XRAY_WRAPPER_FLAG, /* hasPrototype = */ Traits::HasPrototype)
+  : Base(flags | WrapperFactory::IS_XRAY_WRAPPER_FLAG)
 {
+    Base::setHasPrototype(Traits::HasPrototype);
 }
 
 template <typename Base, typename Traits>