diff --git a/include/fast_float/float_common.h b/include/fast_float/float_common.h
index 6ca6beb..9a716d9 100644
--- a/include/fast_float/float_common.h
+++ b/include/fast_float/float_common.h
@@ -1169,7 +1169,7 @@ fastfloat_really_inline constexpr uint8_t max_digits_u64(uint8_t base) {
 
 // If a u64 is exactly max_digits_u64() in length, this is
 // the value below which it has definitely overflowed.
-fastfloat_really_inline constexpr uint8_t min_safe_u64(uint8_t base) {
+fastfloat_really_inline constexpr uint64_t min_safe_u64(uint8_t base) {
   return int_luts<>::min_safe_u64[base - 2];
 }