diff --git a/js/src/jsfriendapi.h b/js/src/jsfriendapi.h
index a930c339d639..1e4cf89c9a69 100644
--- a/js/src/jsfriendapi.h
+++ b/js/src/jsfriendapi.h
@@ -2442,7 +2442,7 @@ FunctionObjectToShadowFunction(JSObject* fun)
 }
 
 /* Statically asserted in jsfun.h. */
-static const unsigned JS_FUNCTION_INTERPRETED_BITS = 0x401;
+static const unsigned JS_FUNCTION_INTERPRETED_BITS = 0x0201;
 
 // Return whether the given function object is native.
 static MOZ_ALWAYS_INLINE bool
diff --git a/js/src/jsfun.h b/js/src/jsfun.h
index 7f026948f441..0b228cb96d3f 100644
--- a/js/src/jsfun.h
+++ b/js/src/jsfun.h
@@ -32,6 +32,7 @@ class JSFunction : public js::NativeObject
         NormalFunction = 0,
         Arrow,                      /* ES6 '(args) => body' syntax */
         Method,                     /* ES6 MethodDefinition */
+        ClassConstructor,
         Getter,
         Setter,
         AsmJS,                      /* function is an asm.js module or exported function */
@@ -52,18 +53,18 @@ class JSFunction : public js::NativeObject
                                        function-statement) */
         SELF_HOSTED      = 0x0080,  /* function is self-hosted builtin and must not be
                                        decompilable nor constructible. */
-        // Free bit
-        HAS_REST         = 0x0200,  /* function has a rest (...) parameter */
-        INTERPRETED_LAZY = 0x0400,  /* function is interpreted but doesn't have a script yet */
-        RESOLVED_LENGTH  = 0x0800,  /* f.length has been resolved (see fun_resolve). */
-        RESOLVED_NAME    = 0x1000,  /* f.name has been resolved (see fun_resolve). */
+        HAS_REST         = 0x0100,  /* function has a rest (...) parameter */
+        INTERPRETED_LAZY = 0x0200,  /* function is interpreted but doesn't have a script yet */
+        RESOLVED_LENGTH  = 0x0400,  /* f.length has been resolved (see fun_resolve). */
+        RESOLVED_NAME    = 0x0800,  /* f.name has been resolved (see fun_resolve). */
 
-        FUNCTION_KIND_SHIFT = 13,
-        FUNCTION_KIND_MASK  = 0x7 << FUNCTION_KIND_SHIFT,
+        FUNCTION_KIND_SHIFT = 12,
+        FUNCTION_KIND_MASK  = 0xf << FUNCTION_KIND_SHIFT,
 
         ASMJS_KIND = AsmJS << FUNCTION_KIND_SHIFT,
         ARROW_KIND = Arrow << FUNCTION_KIND_SHIFT,
         METHOD_KIND = Method << FUNCTION_KIND_SHIFT,
+        CLASSCONSTRUCTOR_KIND = ClassConstructor << FUNCTION_KIND_SHIFT,
         GETTER_KIND = Getter << FUNCTION_KIND_SHIFT,
         SETTER_KIND = Setter << FUNCTION_KIND_SHIFT,
 
@@ -73,7 +74,7 @@ class JSFunction : public js::NativeObject
         ASMJS_CTOR = ASMJS_KIND | NATIVE_CTOR,
         ASMJS_LAMBDA_CTOR = ASMJS_KIND | NATIVE_CTOR | LAMBDA,
         INTERPRETED_METHOD = INTERPRETED | METHOD_KIND,
-        INTERPRETED_CLASS_CONSTRUCTOR = INTERPRETED | METHOD_KIND | CONSTRUCTOR,
+        INTERPRETED_CLASS_CONSTRUCTOR = INTERPRETED | CLASSCONSTRUCTOR_KIND | CONSTRUCTOR,
         INTERPRETED_GETTER = INTERPRETED | GETTER_KIND,
         INTERPRETED_SETTER = INTERPRETED | SETTER_KIND,
         INTERPRETED_LAMBDA = INTERPRETED | LAMBDA | CONSTRUCTOR,
@@ -165,15 +166,12 @@ class JSFunction : public js::NativeObject
     // Arrow functions store their lexical |this| in the first extended slot.
     bool isArrow()                  const { return kind() == Arrow; }
     // Every class-constructor is also a method.
-    bool isMethod()                 const { return kind() == Method; }
+    bool isMethod()                 const { return kind() == Method || kind() == ClassConstructor; }
+    bool isClassConstructor()       const { return kind() == ClassConstructor; }
 
     bool isGetter()                 const { return kind() == Getter; }
     bool isSetter()                 const { return kind() == Setter; }
 
-    bool isClassConstructor() const {
-        return kind() == Method && isConstructor();
-    }
-
     bool allowSuperProperty() const {
         return isMethod() || isGetter() || isSetter();
     }