diff --git a/include/fmt/format.h b/include/fmt/format.h
index 3961ded3..161df54a 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -3522,8 +3522,13 @@ FMT_CONSTEXPR20 auto write(OutputIt out, T value) -> OutputIt {
     } else {
       *ptr++ = static_cast<Char>('0' + significand);
     }
-    memcpy(ptr, prefix, 2);
-    ptr += 2;
+    if (std::is_same<Char, char>::value) {
+      memcpy(ptr, prefix, 2);
+      ptr += 2;
+    } else {
+      *ptr++ = prefix[0];
+      *ptr++ = prefix[1];
+    }
     if (abs_exponent >= 100) {
       *ptr++ = static_cast<Char>('0' + abs_exponent / 100);
       abs_exponent %= 100;
diff --git a/test/xchar-test.cc b/test/xchar-test.cc
index a94c1bd2..a823ca06 100644
--- a/test/xchar-test.cc
+++ b/test/xchar-test.cc
@@ -74,6 +74,7 @@ TEST(xchar_test, format_explicitly_convertible_to_wstring_view) {
 TEST(xchar_test, format) {
   EXPECT_EQ(fmt::format(L"{}", 42), L"42");
   EXPECT_EQ(fmt::format(L"{}", 4.2), L"4.2");
+  EXPECT_EQ(fmt::format(L"{}", 1e100), L"1e+100");
   EXPECT_EQ(fmt::format(L"{}", L"abc"), L"abc");
   EXPECT_EQ(fmt::format(L"{}", L'z'), L"z");
   EXPECT_THROW(fmt::format(fmt::runtime(L"{:*\x343E}"), 42), fmt::format_error);