diff --git a/include/fmt/format.h b/include/fmt/format.h
index 550f607c7cc81..ebf85210a6d61 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -464,7 +464,7 @@ template <typename T> constexpr auto num_bits() -> int {
 }
 // std::numeric_limits<T>::digits may return 0 for 128-bit ints.
 template <> constexpr auto num_bits<int128_opt>() -> int { return 128; }
-template <> constexpr auto num_bits<uint128_t>() -> int { return 128; }
+template <> constexpr auto num_bits<uint128_fallback>() -> int { return 128; }
 
 // A heterogeneous bit_cast used for converting 96-bit long double to uint128_t
 // and 128-bit pointers to uint128_fallback.
diff --git a/test/format-test.cc b/test/format-test.cc
index ad4d7a73657b3..223fb1b3ce10a 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1561,14 +1561,13 @@ TEST(format_test, format_pointer) {
 TEST(format_test, write_uintptr_fallback) {
   // Test that formatting a pointer by converting it to uint128_fallback works.
   // This is needed to support systems without uintptr_t.
-  // TODO
-  /*auto s = std::string();
+  auto s = std::string();
   fmt::detail::write_ptr<char>(
       std::back_inserter(s),
       fmt::detail::bit_cast<fmt::detail::uint128_fallback>(
           reinterpret_cast<void*>(0xface)),
       nullptr);
-  EXPECT_EQ(s, "0xface");*/
+  EXPECT_EQ(s, "0xface");
 }
 
 enum class color { red, green, blue };