diff --git a/mfbt/TypedEnum.h b/mfbt/TypedEnum.h
index 2baae5ea8b2..6f595cb4c5f 100644
--- a/mfbt/TypedEnum.h
+++ b/mfbt/TypedEnum.h
@@ -92,16 +92,33 @@
  * mandatory.  As with MOZ_ENUM_TYPE(), it will do nothing on compilers that do
  * not support it.
  *
- * Note that the workaround implemented here is not compatible with enums
- * nested inside a class.
+ * MOZ_{BEGIN,END}_ENUM_CLASS doesn't work for defining enum classes nested
+ * inside classes.  To define an enum class nested inside another class, use
+ * MOZ_{BEGIN,END}_NESTED_ENUM_CLASS, and place a MOZ_FINISH_NESTED_ENUM_CLASS
+ * in namespace scope to handle bits that can only be implemented with
+ * namespace-scoped code.  For example:
+ *
+ *   class FooBar {
+ *
+ *     MOZ_BEGIN_NESTED_ENUM_CLASS(Enum, int32_t)
+ *       A,
+ *       B = 6
+ *     MOZ_END_NESTED_ENUM_CLASS(Enum)
+ *
+ *   };
+ *
+ *   MOZ_FINISH_NESTED_ENUM_CLASS(FooBar::Enum)
  */
 #if defined(MOZ_HAVE_CXX11_STRONG_ENUMS)
   /*
    * All compilers that support strong enums also support an explicit
    * underlying type, so no extra check is needed.
    */
-#  define MOZ_BEGIN_ENUM_CLASS(Name, type) enum class Name : type {
-#  define MOZ_END_ENUM_CLASS(Name)         };
+#  define MOZ_BEGIN_NESTED_ENUM_CLASS(Name, type) \
+     enum class Name : type {
+#  define MOZ_END_NESTED_ENUM_CLASS(Name) \
+     };
+#  define MOZ_FINISH_NESTED_ENUM_CLASS(Name) /* nothing */
 #else
    /**
     * We need Name to both name a type, and scope the provided enumerator
@@ -137,14 +154,14 @@
     *   {
     *     return Enum::A;
     *   }
-    */
-#  define MOZ_BEGIN_ENUM_CLASS(Name, type) \
+    */\
+#  define MOZ_BEGIN_NESTED_ENUM_CLASS(Name, type) \
      class Name \
      { \
        public: \
          enum Enum MOZ_ENUM_TYPE(type) \
          {
-#  define MOZ_END_ENUM_CLASS(Name) \
+#  define MOZ_END_NESTED_ENUM_CLASS(Name) \
          }; \
          Name() {} \
          Name(Enum aEnum) : mEnum(aEnum) {} \
@@ -152,7 +169,8 @@
          operator Enum() const { return mEnum; } \
        private: \
          Enum mEnum; \
-     }; \
+     };
+#  define MOZ_FINISH_NESTED_ENUM_CLASS(Name) \
      inline int operator+(const int&, const Name::Enum&) MOZ_DELETE; \
      inline int operator+(const Name::Enum&, const int&) MOZ_DELETE; \
      inline int operator-(const int&, const Name::Enum&) MOZ_DELETE; \
@@ -208,6 +226,10 @@
      inline int& operator<<=(int&, const Name::Enum&) MOZ_DELETE; \
      inline int& operator>>=(int&, const Name::Enum&) MOZ_DELETE;
 #endif
+#  define MOZ_BEGIN_ENUM_CLASS(Name, type) MOZ_BEGIN_NESTED_ENUM_CLASS(Name, type)
+#  define MOZ_END_ENUM_CLASS(Name) \
+     MOZ_END_NESTED_ENUM_CLASS(Name) \
+     MOZ_FINISH_NESTED_ENUM_CLASS(Name)
 
 #endif /* __cplusplus */