diff --git a/include/fmt/core.h b/include/fmt/core.h
index e17e0702..10ac2843 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -393,12 +393,6 @@ template <typename Char> constexpr bool is_unicode() {
   return FMT_UNICODE || sizeof(Char) != 1 ||
          (sizeof(micro) == 3 && micro[0] == 0xC2 && micro[1] == 0xB5);
 }
-
-#ifdef __cpp_char8_t
-using char8_type = char8_t;
-#else
-enum char8_type : unsigned char {};
-#endif
 }  // namespace detail
 
 /**
@@ -507,9 +501,6 @@ using wstring_view = basic_string_view<wchar_t>;
 template <typename T> struct is_char : std::false_type {};
 template <> struct is_char<char> : std::true_type {};
 template <> struct is_char<wchar_t> : std::true_type {};
-template <> struct is_char<detail::char8_type> : std::true_type {};
-template <> struct is_char<char16_t> : std::true_type {};
-template <> struct is_char<char32_t> : std::true_type {};
 
 /**
   \rst
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 76fe1444..84a968cd 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -431,6 +431,12 @@ FMT_CONSTEXPR20 T* fill_n(T* out, Size count, char value) {
   return out + count;
 }
 
+#ifdef __cpp_char8_t
+using char8_type = char8_t;
+#else
+enum char8_type : unsigned char {};
+#endif
+
 template <typename InputIt, typename OutChar>
 using needs_conversion = bool_constant<
     std::is_same<typename std::iterator_traits<InputIt>::value_type,
@@ -634,6 +640,10 @@ void iterator_buffer<OutputIt, T, Traits>::flush() {
 
 FMT_MODULE_EXPORT_BEGIN
 
+template <> struct is_char<detail::char8_type> : std::true_type {};
+template <> struct is_char<char16_t> : std::true_type {};
+template <> struct is_char<char32_t> : std::true_type {};
+
 // The number of characters to store in the basic_memory_buffer object itself
 // to avoid dynamic memory allocation.
 enum { inline_buffer_size = 500 };