diff --git a/src/utils.ts b/src/utils.ts
index e584db6..ba76713 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -68,11 +68,11 @@ export function bytesToHex(bytes: Uint8Array): string {
 }
 
 // We use optimized technique to convert hex string to byte array
-const asciis = { _0: 48, _9: 57, _A: 65, _F: 70, _a: 97, _f: 102 } as const;
+const asciis = { _0: 48, _9: 57, A: 65, F: 70, a: 97, f: 102 } as const;
 function asciiToBase16(ch: number): number | undefined {
   if (ch >= asciis._0 && ch <= asciis._9) return ch - asciis._0; // '2' => 50-48
-  if (ch >= asciis._A && ch <= asciis._F) return ch - (asciis._A - 10); // 'B' => 66-(65-10)
-  if (ch >= asciis._a && ch <= asciis._f) return ch - (asciis._a - 10); // 'b' => 98-(97-10)
+  if (ch >= asciis.A && ch <= asciis.F) return ch - (asciis.A - 10); // 'B' => 66-(65-10)
+  if (ch >= asciis.a && ch <= asciis.f) return ch - (asciis.a - 10); // 'b' => 98-(97-10)
   return;
 }
 
diff --git a/test/utils.test.js b/test/utils.test.js
index d5509f8..614983f 100644
--- a/test/utils.test.js
+++ b/test/utils.test.js
@@ -3,7 +3,15 @@ const fc = require('fast-check');
 const { describe, should } = require('micro-should');
 const { optional, integer, gen } = require('./generator');
 const { TYPE_TEST } = require('./utils');
-const { byteSwap, byteSwapIfBE, byteSwap32, isLE, bytesToHex, concatBytes, hexToBytes } = require('../utils');
+const {
+  byteSwap,
+  byteSwapIfBE,
+  byteSwap32,
+  isLE,
+  bytesToHex,
+  concatBytes,
+  hexToBytes,
+} = require('../utils');
 
 describe('utils', () => {
   const staticHexVectors = [