diff --git a/src/index.ts b/src/index.ts
index 959b832..0a7801b 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -34,7 +34,12 @@ export function parse(string: string): Credentials | undefined {
   if (!match) return undefined;
 
   // decode user pass
-  const userPass = base64.decode(match[1]);
+  let userPass: string;
+  try {
+    userPass = base64.decode(match[1]);
+  } catch {
+    return undefined;
+  }
   const colonIndex = userPass.indexOf(':');
   if (colonIndex === -1) return undefined;
 
diff --git a/src/parse-browser.spec.ts b/src/parse-browser.spec.ts
new file mode 100644
index 0000000..a302bc8
--- /dev/null
+++ b/src/parse-browser.spec.ts
@@ -0,0 +1,32 @@
+import { afterAll, assert, beforeAll, describe, it, vi } from 'vitest';
+
+describe.skipIf(!Uint8Array.fromBase64)('parse without Buffer', () => {
+  let parse: typeof import('./index.js').parse;
+
+  beforeAll(async () => {
+    vi.stubGlobal('Buffer', undefined);
+    vi.resetModules();
+    ({ parse } = await import('./index.js'));
+  });
+
+  afterAll(() => {
+    vi.unstubAllGlobals();
+    vi.resetModules();
+  });
+
+  it('should return undefined for invalid base64 characters', () => {
+    assert.strictEqual(parse('Basic .'), undefined);
+    assert.strictEqual(parse('Basic ~'), undefined);
+  });
+
+  it('should return undefined for incomplete base64', () => {
+    assert.strictEqual(parse('Basic Y'), undefined);
+  });
+
+  it('should parse valid credentials', () => {
+    assert.deepEqual(parse('Basic Zm9vOmJhcg=='), {
+      name: 'foo',
+      pass: 'bar',
+    });
+  });
+});