diff --git a/include/fast_float/ascii_number.h b/include/fast_float/ascii_number.h
index d26b7f4..a3dd7c4 100644
--- a/include/fast_float/ascii_number.h
+++ b/include/fast_float/ascii_number.h
@@ -301,7 +301,7 @@ parse_number_string(UC const *p, UC const *pend,
 #ifndef FASTFLOAT_ONLY_POSITIVE_C_NUMBER_WO_INF_NAN
   answer.negative = (*p == UC('-'));
   // C++17 20.19.3.(7.1) explicitly forbids '+' sign here
-  if ((*p == UC('-')) || (uint64_t(options.format & chars_format::allow_leading_plus) &&
+  if ((*p == UC('-')) || (uint8_t(options.format & chars_format::allow_leading_plus) &&
                           !basic_json_fmt && *p == UC('+'))) {
     ++p;
     if (p == pend) {
@@ -385,10 +385,10 @@ parse_number_string(UC const *p, UC const *pend,
   }
   int32_t exp_number = 0; // explicit exponential part
   if (p != pend &&
-      (uint64_t(options.format & chars_format::scientific) &&
+      (uint8_t(options.format & chars_format::scientific) &&
        ((UC('e') == *p) || (UC('E') == *p)))
 #ifndef FASTFLOAT_ONLY_POSITIVE_C_NUMBER_WO_INF_NAN
-   || (uint64_t(options.format & detail::basic_fortran_fmt) &&
+   || (uint8_t(options.format & detail::basic_fortran_fmt) &&
         (UC('d') == *p) || (UC('D') == *p))
 #endif
   ) {
@@ -406,7 +406,7 @@ parse_number_string(UC const *p, UC const *pend,
       }
     }
     if ((p == pend) || !is_integer(*p)) {
-      if (!uint64_t(options.format & chars_format::fixed)) {
+      if (!uint8_t(options.format & chars_format::fixed)) {
         // The exponential part is invalid for scientific notation, so it must
         // be a trailing token for fixed notation. However, fixed notation is
         // disabled, so report a scientific notation error.
@@ -427,8 +427,8 @@ parse_number_string(UC const *p, UC const *pend,
     }
   } else {
     // If it scientific and not fixed, we have to bail out.
-    if (uint64_t(options.format & chars_format::scientific) &&
-        !uint64_t(options.format & chars_format::fixed)) {
+    if (uint8_t(options.format & chars_format::scientific) &&
+        !uint8_t(options.format & chars_format::fixed)) {
       return report_parse_error<UC>(p, parse_error::missing_exponential_part);
     }
   }
@@ -510,7 +510,7 @@ parse_int_string(UC const *p, UC const *pend, T &value,
     return answer;
   }
   if ((*p == UC('-')) ||
-      (uint64_t(options.format & chars_format::allow_leading_plus) &&
+      (uint8_t(options.format & chars_format::allow_leading_plus) &&
        (*p == UC('+')))) {
     ++p;
   }
diff --git a/include/fast_float/fast_float.h b/include/fast_float/fast_float.h
index 4ca1a0a..4c05c2d 100644
--- a/include/fast_float/fast_float.h
+++ b/include/fast_float/fast_float.h
@@ -43,7 +43,7 @@ from_chars(UC const *first, UC const *last, T &value,
 template <typename T, typename UC = char>
 FASTFLOAT_CONSTEXPR20 from_chars_result_t<UC>
 from_chars_advanced(UC const *first, UC const *last, T &value,
-                    parse_options_t<UC> const &options) noexcept;
+                    parse_options_t<UC> const options) noexcept;
 
 /**
  * from_chars for integer types.
diff --git a/include/fast_float/parse_number.h b/include/fast_float/parse_number.h
index 3bc40a0..93c28a1 100644
--- a/include/fast_float/parse_number.h
+++ b/include/fast_float/parse_number.h
@@ -310,7 +310,7 @@ from_chars_float_advanced(UC const *first, UC const *last, T &value,
 
   from_chars_result_t<UC> answer;
 #ifndef FASTFLOAT_ONLY_POSITIVE_C_NUMBER_WO_INF_NAN
-  if (uint64_t(options.format & chars_format::skip_white_space)) {
+  if (uint8_t(options.format & chars_format::skip_white_space)) {
     while ((first != last) && fast_float::is_space(*first)) {
       first++;
     }
@@ -326,14 +326,14 @@ from_chars_float_advanced(UC const *first, UC const *last, T &value,
 #endif
   parsed_number_string_t<UC> const pns =
 #ifndef FASTFLOAT_ONLY_POSITIVE_C_NUMBER_WO_INF_NAN
-      uint64_t(options.format & detail::basic_json_fmt)
+      uint8_t(options.format & detail::basic_json_fmt)
           ? parse_number_string<true, UC>(first, last, options)
           :
 #endif
           parse_number_string<false, UC>(first, last, options);
   if (!pns.valid) {
 #ifndef FASTFLOAT_ONLY_POSITIVE_C_NUMBER_WO_INF_NAN
-    if (uint64_t(options.format & chars_format::no_infnan)) {
+    if (uint8_t(options.format & chars_format::no_infnan)) {
 #endif
       answer.ec = std::errc::invalid_argument;
       answer.ptr = first;
@@ -373,7 +373,7 @@ from_chars_int_advanced(UC const *first, UC const *last, T &value,
                 "only char, wchar_t, char16_t and char32_t are supported");
 
 #ifndef FASTFLOAT_ONLY_POSITIVE_C_NUMBER_WO_INF_NAN
-  if (uint64_t(options.format & chars_format::skip_white_space)) {
+  if (uint8_t(options.format & chars_format::skip_white_space)) {
     while ((first != last) && fast_float::is_space(*first)) {
       first++;
     }
@@ -387,6 +387,7 @@ from_chars_int_advanced(UC const *first, UC const *last, T &value,
 #else
   // We are in parser code with external loop that checks bounds.
   FASTFLOAT_ASSUME(first < last);
+  // base is already checked in the parse_options_t constructor.
 #endif
 
   return parse_int_string(first, last, value, options);