diff --git a/lib/buffer.js b/lib/buffer.js
index c9f45d333886d3..7cce07ddc5d410 100644
--- a/lib/buffer.js
+++ b/lib/buffer.js
@@ -99,6 +99,8 @@ const {
   inspect: utilInspect,
 } = require('internal/util/inspect');
 
+const assert = require('internal/assert');
+
 const {
   codes: {
     ERR_BUFFER_OUT_OF_BOUNDS,
@@ -1302,9 +1304,9 @@ function atob(input) {
       throw lazyDOMException(
         'The string to be decoded is not correctly encoded.',
         'InvalidCharacterError');
-    case -3: // Possible overflow
-      // TODO(@anonrig): Throw correct error in here.
-      throw lazyDOMException('The input causes overflow.', 'InvalidCharacterError');
+    case -3:
+      assert.fail('Unrecognized simdutf error');
+      break;
     default:
       return result;
   }