diff --git a/index.js b/index.js
index 61581545..a4cabab0 100644
--- a/index.js
+++ b/index.js
@@ -50,6 +50,8 @@ function is(x) {
         // Languages
         "thirteen", // English
         "ثلاثة عشر", // Arabic
+        "سیزده", // Persian
+        "۱۳", // Persian number
         "dertien", // Afrikaans / Dutch
         "dertiendertien", // Double Dutch
         "тринадесет", // Bulgarian