diff --git a/package.json b/package.json
index a912c032a..28972e774 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "validator",
   "description": "String validation and sanitization",
-  "version": "13.6.0",
+  "version": "13.6.1",
   "sideEffects": false,
   "homepage": "https://github.com/validatorjs/validator.js",
   "files": [
diff --git a/src/lib/isUUID.js b/src/lib/isUUID.js
index 61d938ac3..0174ae745 100644
--- a/src/lib/isUUID.js
+++ b/src/lib/isUUID.js
@@ -7,8 +7,15 @@ const uuid = {
   all: /^[0-9A-F]{8}-[0-9A-F]{4}-[0-9A-F]{4}-[0-9A-F]{4}-[0-9A-F]{12}$/i,
 };
 
-export default function isUUID(str, version = 'all') {
+function extractUUIDVersion(version) {
+  const isKnownVersion = Object.keys(uuid).includes(String(version));
+  if (isKnownVersion) return version;
+  return version ? undefined : 'all';
+}
+
+export default function isUUID(str, version) {
   assertString(str);
-  const pattern = uuid[version];
+  const uuidVersion = extractUUIDVersion(version);
+  const pattern = uuid[uuidVersion];
   return pattern && pattern.test(str);
 }
diff --git a/test/validators.js b/test/validators.js
index 91794d521..12db2030f 100644
--- a/test/validators.js
+++ b/test/validators.js
@@ -4413,6 +4413,24 @@ describe('Validators', () => {
         'AAAAAAAA-1111-1111-AAAG-111111111111',
       ],
     });
+    test({
+      validator: 'isUUID',
+      args: [null],
+      valid: [
+        'A117FBC9-4BED-3078-CF07-9141BA07C9F3',
+        'A117FBC9-4BED-4078-8F07-9141BA07C9F3',
+        'A117FBC9-4BED-5078-AF07-9141BA07C9F3',
+      ],
+      invalid: [
+        '',
+        'xxxA987FBC9-4BED-3078-CF07-9141BA07C9F3',
+        'A117FBC9-4BED-3078-CF07-9141BA07C9F3xxx',
+        'A117FBC94BED3078CF079141BA07C9F3',
+        '911859',
+        '911FBC9-4BED-3078-CF07A-9141BA07C9F3',
+        'A11AAAAA-1111-1111-AAAG-111111111111',
+      ],
+    });
     test({
       validator: 'isUUID',
       args: [3],