diff --git a/src/abstract/hash-to-curve.ts b/src/abstract/hash-to-curve.ts
index 64d7db4..3bebb95 100644
--- a/src/abstract/hash-to-curve.ts
+++ b/src/abstract/hash-to-curve.ts
@@ -1,7 +1,8 @@
 /*! noble-curves - MIT License (c) 2022 Paul Miller (paulmillr.com) */
 import type { Group, GroupConstructor, AffinePoint } from './curve.js';
 import { mod, IField } from './modular.js';
-import { bytesToNumberBE, CHash, concatBytes, utf8ToBytes, validateObject } from './utils.js';
+import type { CHash } from './utils.js';
+import { bytesToNumberBE, isBytes, concatBytes, utf8ToBytes, validateObject } from './utils.js';
 
 /**
  * * `DST` is a domain separation tag, defined in section 2.2.5
@@ -22,7 +23,7 @@ export type Opts = {
 };
 
 function validateDST(dst: UnicodeOrBytes): Uint8Array {
-  if (dst instanceof Uint8Array) return dst;
+  if (isBytes(dst)) return dst;
   if (typeof dst === 'string') return utf8ToBytes(dst);
   throw new Error('DST must be Uint8Array or string');
 }
@@ -51,8 +52,8 @@ function strxor(a: Uint8Array, b: Uint8Array): Uint8Array {
   return arr;
 }
 
-function isBytes(item: unknown): void {
-  if (!(item instanceof Uint8Array)) throw new Error('Uint8Array expected');
+function abytes(item: unknown): void {
+  if (!isBytes(item)) throw new Error('Uint8Array expected');
 }
 function isNum(item: unknown): void {
   if (!Number.isSafeInteger(item)) throw new Error('number expected');
@@ -66,8 +67,8 @@ export function expand_message_xmd(
   lenInBytes: number,
   H: CHash
 ): Uint8Array {
-  isBytes(msg);
-  isBytes(DST);
+  abytes(msg);
+  abytes(DST);
   isNum(lenInBytes);
   // https://www.rfc-editor.org/rfc/rfc9380#section-5.3.3
   if (DST.length > 255) DST = H(concatBytes(utf8ToBytes('H2C-OVERSIZE-DST-'), DST));
@@ -100,8 +101,8 @@ export function expand_message_xof(
   k: number,
   H: CHash
 ): Uint8Array {
-  isBytes(msg);
-  isBytes(DST);
+  abytes(msg);
+  abytes(DST);
   isNum(lenInBytes);
   // https://www.rfc-editor.org/rfc/rfc9380#section-5.3.3
   // DST = H('H2C-OVERSIZE-DST-' || a_very_long_DST, Math.ceil((lenInBytes * k) / 8));
@@ -139,7 +140,7 @@ export function hash_to_field(msg: Uint8Array, count: number, options: Opts): bi
     hash: 'hash',
   });
   const { p, k, m, hash, expand, DST: _DST } = options;
-  isBytes(msg);
+  abytes(msg);
   isNum(count);
   const DST = validateDST(_DST);
   const log2p = p.toString(2).length;
diff --git a/src/abstract/weierstrass.ts b/src/abstract/weierstrass.ts
index cb5c938..f66f2bb 100644
--- a/src/abstract/weierstrass.ts
+++ b/src/abstract/weierstrass.ts
@@ -158,7 +158,7 @@ export const DER = {
     // parse DER signature
     const { Err: E } = DER;
     const data = typeof hex === 'string' ? h2b(hex) : hex;
-    if (!(data instanceof Uint8Array)) throw new Error('ui8a expected');
+    if (!ut.isBytes(data)) throw new Error('ui8a expected');
     let l = data.length;
     if (l < 2 || data[0] != 0x30) throw new E('Invalid signature tag');
     if (data[1] !== l - 2) throw new E('Invalid signature: incorrect length');
@@ -238,7 +238,7 @@ export function weierstrassPoints<T>(opts: CurvePointsType<T>): CurvePointsRes<T
   function normPrivateKeyToScalar(key: PrivKey): bigint {
     const { allowedPrivateKeyLengths: lengths, nByteLength, wrapPrivateKey, n } = CURVE;
     if (lengths && typeof key !== 'bigint') {
-      if (key instanceof Uint8Array) key = ut.bytesToHex(key);
+      if (ut.isBytes(key)) key = ut.bytesToHex(key);
       // Normalize to hex string, pad. E.g. P521 would norm 130-132 char hex to 132-char bytes
       if (typeof key !== 'string' || !lengths.includes(key.length)) throw new Error('Invalid key');
       key = key.padStart(nByteLength * 2, '0');
@@ -893,7 +893,7 @@ export function weierstrass(curveDef: CurveType): CurveFn {
    * Quick and dirty check for item being public key. Does not validate hex, or being on-curve.
    */
   function isProbPub(item: PrivKey | PubKey): boolean {
-    const arr = item instanceof Uint8Array;
+    const arr = ut.isBytes(item);
     const str = typeof item === 'string';
     const len = (arr || str) && (item as Hex).length;
     if (arr) return len === compressedLen || len === uncompressedLen;
@@ -1057,7 +1057,7 @@ export function weierstrass(curveDef: CurveType): CurveFn {
     let _sig: Signature | undefined = undefined;
     let P: ProjPointType<bigint>;
     try {
-      if (typeof sg === 'string' || sg instanceof Uint8Array) {
+      if (typeof sg === 'string' || ut.isBytes(sg)) {
         // Signature can be represented in 2 ways: compact (2*nByteLength) & DER (variable-length).
         // Since DER can also be 2*nByteLength bytes, we check for it first.
         try {