diff --git a/include/fast_float/parse_number.h b/include/fast_float/parse_number.h
index 8a310ce..f7096a6 100644
--- a/include/fast_float/parse_number.h
+++ b/include/fast_float/parse_number.h
@@ -197,7 +197,7 @@ from_chars(UC const *first, UC const *last, T &value,
 
 template <typename T>
 fastfloat_really_inline FASTFLOAT_CONSTEXPR20 bool
-clinger_fast_path_impl(uint64_t const mantissa, int64_t const exponent,
+clinger_fast_path_impl(am_mant_t const mantissa, am_pow_t const exponent,
 #ifndef FASTFLOAT_ONLY_POSITIVE_C_NUMBER_WO_INF_NAN
                        bool const is_negative,
 #endif