diff --git a/packages/uint8arrays/src/lib/uint8arrays.spec.ts b/packages/uint8arrays/src/lib/uint8arrays.spec.ts
index f00907917d..329c9c169f 100644
--- a/packages/uint8arrays/src/lib/uint8arrays.spec.ts
+++ b/packages/uint8arrays/src/lib/uint8arrays.spec.ts
@@ -187,4 +187,12 @@ describe('turn to base64urlpad', () => {
 
     expect(base64).toBe('SGVsbG8sIFdvcmxkIQ');
   });
+
+  it('should replace every base64url character when encoding and decoding', () => {
+    const bytes = new Uint8Array([251, 239, 255, 251, 239, 255]);
+    const encoded = uint8arrayToString(bytes, 'base64urlpad');
+
+    expect(encoded).toBe('--__--__');
+    expect(uint8arrayFromString(encoded, 'base64urlpad')).toEqual(bytes);
+  });
 });
diff --git a/packages/uint8arrays/src/lib/uint8arrays.ts b/packages/uint8arrays/src/lib/uint8arrays.ts
index 186111648d..3b755d4965 100644
--- a/packages/uint8arrays/src/lib/uint8arrays.ts
+++ b/packages/uint8arrays/src/lib/uint8arrays.ts
@@ -121,13 +121,13 @@ export function uint8ArrayToBase64(uint8Array: Uint8Array): string {
 
 function base64UrlPadToBase64(base64UrlPadStr: string): string {
   return (
-    base64UrlPadStr.replace('-', '+').replace('_', '/') +
+    base64UrlPadStr.replace(/-/g, '+').replace(/_/g, '/') +
     '='.repeat((4 - (base64UrlPadStr.length % 4)) % 4)
   );
 }
 
 function base64ToBase64UrlPad(base64Str: string): string {
-  return base64Str.replace('+', '-').replace('/', '_').replace(/=+$/, '');
+  return base64Str.replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '');
 }
 
 export function uint8arrayFromString(