--- a/mfbt/TypeTraits.h
+++ b/mfbt/TypeTraits.h
@@ -41,17 +41,17 @@ typename AddRvalueReference<T>::Type Dec
 
 /**
  * Helper class used as a base for various type traits, exposed publicly
  * because <type_traits> exposes it as well.
  */
 template<typename T, T Value>
 struct IntegralConstant
 {
-  static const T value = Value;
+  static constexpr T value = Value;
   typedef T ValueType;
   typedef IntegralConstant<T, Value> Type;
 };
 
 /** Convenient aliases. */
 typedef IntegralConstant<bool, true> TrueType;
 typedef IntegralConstant<bool, false> FalseType;