--- a/js/src/frontend/EitherParser.h
+++ b/js/src/frontend/EitherParser.h
@@ -8,17 +8,16 @@
  * A variant-like class abstracting operations on a Parser with a given ParseHandler but
  * unspecified character type.
  */
 
 #ifndef frontend_EitherParser_h
 #define frontend_EitherParser_h
 
 #include "mozilla/Attributes.h"
-#include "mozilla/IndexSequence.h"
 #include "mozilla/Move.h"
 #include "mozilla/Tuple.h"
 #include "mozilla/TypeTraits.h"
 #include "mozilla/Variant.h"
 
 #include "frontend/Parser.h"
 #include "frontend/TokenStream.h"
 
@@ -30,17 +29,17 @@ template<template <class Parser> class G
          template <class This> class MemberFunction,
          typename... Args>
 struct InvokeMemberFunction
 {
     mozilla::Tuple<typename mozilla::Decay<Args>::Type...> args;
 
     template<class This, size_t... Indices>
     auto
-    matchInternal(This* obj, mozilla::IndexSequence<Indices...>)
+    matchInternal(This* obj, std::index_sequence<Indices...>)
       -> decltype(((*obj).*(MemberFunction<This>::get()))(mozilla::Get<Indices>(args)...))
     {
         return ((*obj).*(MemberFunction<This>::get()))(mozilla::Get<Indices>(args)...);
     }
 
   public:
     template<typename... ActualArgs>
     explicit InvokeMemberFunction(ActualArgs&&... actualArgs)