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;
   }
diff --git a/src/node_buffer.cc b/src/node_buffer.cc
index 0e4d437c1ea501..8dd88948cb827f 100644
--- a/src/node_buffer.cc
+++ b/src/node_buffer.cc
@@ -1341,7 +1341,7 @@ static void Btoa(const FunctionCallbackInfo<Value>& args) {
 // In case of error, a negative value is returned:
 // * -1 indicates a single character remained,
 // * -2 indicates an invalid character,
-// * -3 indicates a possible overflow (i.e., more than 2 GB output).
+// * -3 indicates an unrecognized simdutf error.
 static void Atob(const FunctionCallbackInfo<Value>& args) {
   CHECK_EQ(args.Length(), 1);
   Environment* env = Environment::GetCurrent(args);
@@ -1386,7 +1386,7 @@ static void Atob(const FunctionCallbackInfo<Value>& args) {
     return args.GetReturnValue().Set(value);
   }
 
-  // Default value is: "possible overflow"
+  // Default value is: "unrecognized simdutf error"
   int32_t error_code = -3;
 
   if (result.error == simdutf::error_code::INVALID_BASE64_CHARACTER) {