diff --git a/src/json.hpp b/src/json.hpp
index 363cb11c2..efcb192ff 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -183,8 +183,8 @@ template <
     template<typename U, typename... Args> class ArrayType = std::vector,
     class StringType = std::string,
     class BooleanType = bool,
-    class NumberIntegerType = int64_t,
-    class NumberUnsignedType = uint64_t,
+    class NumberIntegerType = std::int64_t,
+    class NumberUnsignedType = std::uint64_t,
     class NumberFloatType = double,
     template<typename U> class AllocatorType = std::allocator
     >
diff --git a/src/json.hpp.re2c b/src/json.hpp.re2c
index af2823e4e..612ca2037 100644
--- a/src/json.hpp.re2c
+++ b/src/json.hpp.re2c
@@ -183,8 +183,8 @@ template <
     template<typename U, typename... Args> class ArrayType = std::vector,
     class StringType = std::string,
     class BooleanType = bool,
-    class NumberIntegerType = int64_t,
-    class NumberUnsignedType = uint64_t,
+    class NumberIntegerType = std::int64_t,
+    class NumberUnsignedType = std::uint64_t,
     class NumberFloatType = double,
     template<typename U> class AllocatorType = std::allocator
     >