diff --git a/src/lib/isEmail.js b/src/lib/isEmail.js
index abe465052..ce5b732c1 100644
--- a/src/lib/isEmail.js
+++ b/src/lib/isEmail.js
@@ -168,6 +168,14 @@ export default function isEmail(str, options) {
 
   if (user[0] === '"' && user[user.length - 1] === '"') {
     user = user.slice(1, user.length - 1);
+
+    if (
+      !options.allow_utf8_local_part &&
+    Buffer.byteLength(user, 'utf8') !== user.length
+    ) {
+      return false;
+    }
+
     return options.allow_utf8_local_part ?
       quotedEmailUserUtf8.test(user) :
       quotedEmailUser.test(user);
diff --git a/test/validators.test.js b/test/validators.test.js
index 9bd00d6ec..b5971dc59 100644
--- a/test/validators.test.js
+++ b/test/validators.test.js
@@ -134,6 +134,8 @@ describe('Validators', () => {
         'z@co.c',
         'tüst@invalid.com',
         'nbsp test@test.com',
+        '"tüst"@example.com',
+        '"m端ller"@example.com',
       ],
     });
   });