diff --git a/README.md b/README.md
index 0c2f5d5..82725ee 100644
--- a/README.md
+++ b/README.md
@@ -482,7 +482,7 @@ float: 12345678 * 10^23 = 1.23456782e+30 (==expected)
 ```
 
 Overloads of `fast_float::integer_times_pow10()` are provided for
-signed and unsigned integer types: `int64_t`, `uint64_t`, etc.
+signed and unsigned integer types up to 64 bits: `int64_t`, `uint64_t`, etc.
 
 
 ## Users and Related Work
diff --git a/include/fast_float/parse_number.h b/include/fast_float/parse_number.h
index d12a442..2058330 100644
--- a/include/fast_float/parse_number.h
+++ b/include/fast_float/parse_number.h
@@ -535,38 +535,42 @@ integer_times_pow10(int64_t mantissa, int decimal_exponent) noexcept {
 // the following overloads are here to avoid surprising ambiguity for int,
 // unsigned, etc.
 template <typename T, typename Int>
-FASTFLOAT_CONSTEXPR20
-    typename std::enable_if<is_supported_float_type<T>::value &&
-                                std::is_integral<Int>::value &&
-                                !std::is_signed<Int>::value,
-                            T>::type
-    integer_times_pow10(Int mantissa, int decimal_exponent) noexcept {
+FASTFLOAT_CONSTEXPR20 typename std::enable_if<
+    is_supported_float_type<T>::value && std::is_integral<Int>::value &&
+        sizeof(Int) <= sizeof(uint64_t) && !std::is_signed<Int>::value,
+    T>::type
+integer_times_pow10(Int mantissa, int decimal_exponent) noexcept {
   return integer_times_pow10<T>(static_cast<uint64_t>(mantissa),
                                 decimal_exponent);
 }
 
 template <typename T, typename Int>
-FASTFLOAT_CONSTEXPR20
-    typename std::enable_if<is_supported_float_type<T>::value &&
-                                std::is_integral<Int>::value &&
-                                std::is_signed<Int>::value,
-                            T>::type
-    integer_times_pow10(Int mantissa, int decimal_exponent) noexcept {
+FASTFLOAT_CONSTEXPR20 typename std::enable_if<
+    is_supported_float_type<T>::value && std::is_integral<Int>::value &&
+        sizeof(Int) <= sizeof(int64_t) && std::is_signed<Int>::value,
+    T>::type
+integer_times_pow10(Int mantissa, int decimal_exponent) noexcept {
   return integer_times_pow10<T>(static_cast<int64_t>(mantissa),
                                 decimal_exponent);
 }
 
 template <typename Int>
-FASTFLOAT_CONSTEXPR20 typename std::enable_if<
-    std::is_integral<Int>::value && !std::is_signed<Int>::value, double>::type
-integer_times_pow10(Int mantissa, int decimal_exponent) noexcept {
+FASTFLOAT_CONSTEXPR20
+    typename std::enable_if<std::is_integral<Int>::value &&
+                                sizeof(Int) <= sizeof(uint64_t) &&
+                                !std::is_signed<Int>::value,
+                            double>::type
+    integer_times_pow10(Int mantissa, int decimal_exponent) noexcept {
   return integer_times_pow10(static_cast<uint64_t>(mantissa), decimal_exponent);
 }
 
 template <typename Int>
-FASTFLOAT_CONSTEXPR20 typename std::enable_if<
-    std::is_integral<Int>::value && std::is_signed<Int>::value, double>::type
-integer_times_pow10(Int mantissa, int decimal_exponent) noexcept {
+FASTFLOAT_CONSTEXPR20
+    typename std::enable_if<std::is_integral<Int>::value &&
+                                sizeof(Int) <= sizeof(int64_t) &&
+                                std::is_signed<Int>::value,
+                            double>::type
+    integer_times_pow10(Int mantissa, int decimal_exponent) noexcept {
   return integer_times_pow10(static_cast<int64_t>(mantissa), decimal_exponent);
 }
 
diff --git a/tests/basictest.cpp b/tests/basictest.cpp
index 8ae74fc..44c1e30 100644
--- a/tests/basictest.cpp
+++ b/tests/basictest.cpp
@@ -2283,6 +2283,38 @@ void verify_integer_times_pow10(Int mantissa, int decimal_exponent) {
 }
 } // namespace all_supported_types
 
+#if defined(__SIZEOF_INT128__)
+template <typename Int, typename = void>
+struct has_integer_times_pow10 : std::false_type {};
+
+template <typename Int>
+struct has_integer_times_pow10<
+    Int, std::void_t<decltype(fast_float::integer_times_pow10(Int{}, 0))>>
+    : std::true_type {};
+
+template <typename Float, typename Int, typename = void>
+struct has_typed_integer_times_pow10 : std::false_type {};
+
+template <typename Float, typename Int>
+struct has_typed_integer_times_pow10<
+    Float, Int,
+    std::void_t<decltype(fast_float::integer_times_pow10<Float>(Int{}, 0))>>
+    : std::true_type {};
+
+TEST_CASE("integer_times_pow10 rejects integers wider than 64 bits") {
+  CHECK(has_integer_times_pow10<int64_t>::value);
+  CHECK(has_integer_times_pow10<uint64_t>::value);
+  CHECK(has_typed_integer_times_pow10<float, int64_t>::value);
+  CHECK(has_typed_integer_times_pow10<double, uint64_t>::value);
+  CHECK_FALSE(has_integer_times_pow10<__int128_t>::value);
+  CHECK_FALSE(has_integer_times_pow10<__uint128_t>::value);
+  CHECK_FALSE(has_typed_integer_times_pow10<float, __int128_t>::value);
+  CHECK_FALSE(has_typed_integer_times_pow10<float, __uint128_t>::value);
+  CHECK_FALSE(has_typed_integer_times_pow10<double, __int128_t>::value);
+  CHECK_FALSE(has_typed_integer_times_pow10<double, __uint128_t>::value);
+}
+#endif
+
 TEST_CASE("integer_times_pow10") {
   /* explicitly verifying API with different types of integers */
   // double (the "default" overload)