diff --git a/include/fast_float/ascii_number.h b/include/fast_float/ascii_number.h
index cac91606..5609ba1a 100644
--- a/include/fast_float/ascii_number.h
+++ b/include/fast_float/ascii_number.h
@@ -42,6 +42,11 @@ fastfloat_really_inline constexpr uint64_t byteswap(uint64_t val) {
          (val & 0x000000000000FF00) << 40 | (val & 0x00000000000000FF) << 56;
 }
 
+fastfloat_really_inline constexpr uint32_t byteswap_32(uint32_t val) {
+  return (val >> 24) | ((val >> 8) & 0x0000FF00u) | ((val << 8) & 0x00FF0000u) |
+         (val << 24);
+}
+
 // Read 8 UC into a u64. Truncates UC if not char.
 template <typename UC>
 fastfloat_really_inline FASTFLOAT_CONSTEXPR20 uint64_t
@@ -510,97 +515,95 @@ parse_int_string(UC const *p, UC const *pend, T &value,
   UC const *const start_digits = p;
 
   FASTFLOAT_IF_CONSTEXPR17((std::is_same<T, std::uint8_t>::value)) {
-    const size_t len = (size_t)(pend - p);
-    if (len == 0) {
-      if (has_leading_zeros) {
-        value = 0;
-        answer.ec = std::errc();
-        answer.ptr = p;
-      } else {
-        answer.ec = std::errc::invalid_argument;
-        answer.ptr = first;
+    if (base == 10) {
+      const size_t len = (size_t)(pend - p);
+      if (len == 0) {
+        if (has_leading_zeros) {
+          value = 0;
+          answer.ec = std::errc();
+          answer.ptr = p;
+        } else {
+          answer.ec = std::errc::invalid_argument;
+          answer.ptr = first;
+        }
+        return answer;
       }
-      return answer;
-    }
 
-    uint32_t digits;
+      uint32_t digits;
 
 #if FASTFLOAT_HAS_IS_CONSTANT_EVALUATED && FASTFLOAT_HAS_BIT_CAST
-    if (std::is_constant_evaluated()) {
-      uint8_t str[4]{};
-      for (size_t j = 0; j < 4 && j < len; ++j) {
-        str[j] = static_cast<uint8_t>(p[j]);
-      }
-      digits = std::bit_cast<uint32_t>(str);
+      if (std::is_constant_evaluated()) {
+        uint8_t str[4]{};
+        for (size_t j = 0; j < 4 && j < len; ++j) {
+          str[j] = static_cast<uint8_t>(p[j]);
+        }
+        digits = std::bit_cast<uint32_t>(str);
 #if FASTFLOAT_IS_BIG_ENDIAN
-      digits = byteswap(digits);
+        digits = byteswap_32(digits);
 #endif
-    }
+      }
 #else
-    if (false) {
-    }
-#endif
-    else if (len >= 4) {
-      ::memcpy(&digits, p, 4);
-#if FASTFLOAT_IS_BIG_ENDIAN
-      digits = byteswap(digits);
+      if (false) {
+      }
 #endif
-    } else {
-      uint32_t b0 = static_cast<uint8_t>(p[0]);
-      uint32_t b1 = (len > 1) ? static_cast<uint8_t>(p[1]) : 0xFFu;
-      uint32_t b2 = (len > 2) ? static_cast<uint8_t>(p[2]) : 0xFFu;
-      uint32_t b3 = 0xFFu;
+      else if (len >= 4) {
+        ::memcpy(&digits, p, 4);
 #if FASTFLOAT_IS_BIG_ENDIAN
-      digits = (b0 << 24) | (b1 << 16) | (b2 << 8) | b3;
-#else
-      digits = b0 | (b1 << 8) | (b2 << 16) | (b3 << 24);
+        digits = byteswap_32(digits);
 #endif
-    }
+      } else {
+        uint32_t b0 = static_cast<uint8_t>(p[0]);
+        uint32_t b1 = (len > 1) ? static_cast<uint8_t>(p[1]) : 0xFFu;
+        uint32_t b2 = (len > 2) ? static_cast<uint8_t>(p[2]) : 0xFFu;
+        uint32_t b3 = 0xFFu;
+        digits = b0 | (b1 << 8) | (b2 << 16) | (b3 << 24);
+      }
 
-    uint32_t magic =
-        ((digits + 0x46464646u) | (digits - 0x30303030u)) & 0x80808080u;
-    uint32_t tz = (uint32_t)countr_zero_32(magic); // 7, 15, 23, 31, or 32
-    uint32_t nd = (tz == 32) ? 4 : (tz >> 3);
-    nd = (uint32_t)std::min((size_t)nd, len);
-    if (nd == 0) {
-      if (has_leading_zeros) {
-        value = 0;
-        answer.ec = std::errc();
-        answer.ptr = p;
+      uint32_t magic =
+          ((digits + 0x46464646u) | (digits - 0x30303030u)) & 0x80808080u;
+      uint32_t tz = (uint32_t)countr_zero_32(magic); // 7, 15, 23, 31, or 32
+      uint32_t nd = (tz == 32) ? 4 : (tz >> 3);
+      nd = (uint32_t)std::min((size_t)nd, len);
+      if (nd == 0) {
+        if (has_leading_zeros) {
+          value = 0;
+          answer.ec = std::errc();
+          answer.ptr = p;
+          return answer;
+        }
+        answer.ec = std::errc::invalid_argument;
+        answer.ptr = first;
         return answer;
       }
-      answer.ec = std::errc::invalid_argument;
-      answer.ptr = first;
-      return answer;
-    }
-    if (nd > 3) {
-      const UC *q = p + nd;
-      size_t rem = len - nd;
-      while (rem) {
-        if (*q < UC('0') || *q > UC('9'))
-          break;
-        ++q;
-        --rem;
+      if (nd > 3) {
+        const UC *q = p + nd;
+        size_t rem = len - nd;
+        while (rem) {
+          if (*q < UC('0') || *q > UC('9'))
+            break;
+          ++q;
+          --rem;
+        }
+        answer.ec = std::errc::result_out_of_range;
+        answer.ptr = q;
+        return answer;
       }
-      answer.ec = std::errc::result_out_of_range;
-      answer.ptr = q;
-      return answer;
-    }
 
-    digits ^= 0x30303030u;
-    digits <<= ((4 - nd) * 8);
+      digits ^= 0x30303030u;
+      digits <<= ((4 - nd) * 8);
 
-    uint32_t check = ((digits >> 24) & 0xff) | ((digits >> 8) & 0xff00) |
-                     ((digits << 8) & 0xff0000);
-    if (check > 0x00020505) {
-      answer.ec = std::errc::result_out_of_range;
+      uint32_t check = ((digits >> 24) & 0xff) | ((digits >> 8) & 0xff00) |
+                       ((digits << 8) & 0xff0000);
+      if (check > 0x00020505) {
+        answer.ec = std::errc::result_out_of_range;
+        answer.ptr = p + nd;
+        return answer;
+      }
+      value = (uint8_t)((0x640a01 * digits) >> 24);
+      answer.ec = std::errc();
       answer.ptr = p + nd;
       return answer;
     }
-    value = (uint8_t)((0x640a01 * digits) >> 24);
-    answer.ec = std::errc();
-    answer.ptr = p + nd;
-    return answer;
   }
 
   uint64_t i = 0;