diff --git a/trademark/models.py b/trademark/models.py
index 3090784..75d21d8 100644
--- a/trademark/models.py
+++ b/trademark/models.py
@@ -49,7 +49,7 @@ class Nice(models.Model):
 
 class Trademark(models.Model):
     title = models.CharField(max_length=255)
-    ext_id = models.CharField()
+    ext_id = models.CharField(max_length=20)
     application_id = models.IntegerField()
     cert_id = models.IntegerField()
     owner = models.ForeignKey(Owner)