diff --git a/ext/tm/include/tm/string.hpp b/ext/tm/include/tm/string.hpp
index 0df4f274d9..16212cb823 100644
--- a/ext/tm/include/tm/string.hpp
+++ b/ext/tm/include/tm/string.hpp
@@ -1577,6 +1577,20 @@ class String final {
      * auto str = String::format("{} {}orld {}", cstr, c, num);
      * assert_str_eq("hello world 999", str);
      * ```
+     *
+     * Using `{h}`, an integral value or a pointer can be displayed as hex
+     * ```
+     * void *ptr = nullptr;
+     * int i = 255;
+     * auto str = String::format("Pointer = {h}, Integer = {h}", ptr, i);
+     * assert_str_eq("Pointer = 0x0, Integer = 0xff", str);
+     * ```
+     *
+     * A floating point in hex mode is floored to the integer value.
+     * ```should_abort
+     * float f = 10.5;
+     * String::format("{h}", f);
+     * ```
      */
     template <typename... Args>
     static String format(const char *const fmt, Args... args) {
@@ -1595,7 +1609,7 @@ class String final {
     static void format(String &out, const char *fmt, T first, Args... rest) {
         for (const char *c = fmt; *c != 0; c++) {
             if (*c == '{' && *(c + 1) == 'h' && *(c + 2) == '}') {
-                if constexpr (std::is_arithmetic<T>::value || std::is_pointer<T>::value) {
+                if constexpr (std::is_integral_v<T> || std::is_pointer_v<T>) {
                     out += hex(first, HexFormat::LowercaseAndPrefixed);
                     format(out, c + 3, rest...);
                     return;
@@ -1604,7 +1618,7 @@ class String final {
                     abort();
                 }
             } else if (*c == '{' && *(c + 1) == '}') {
-                if constexpr (std::is_pointer<T>::value && !std::is_same<const char *, T>::value && !std::is_same<char *, T>::value) {
+                if constexpr (std::is_pointer_v<T> && !std::is_same_v<const char *, T> && !std::is_same_v<char *, T>) {
                     fprintf(stderr, "String::format: T is a general pointer type but you didn't specify {h}\n");
                     abort();
                 } else {