diff --git a/src/Entity/Offering.php b/src/Entity/Offering.php
index 9aa13bc..6f8ac66 100644
--- a/src/Entity/Offering.php
+++ b/src/Entity/Offering.php
@@ -43,7 +43,7 @@ class Offering
     /**
      * @ORM\Column(type="integer")
      */
-    #[Assert\NotBlank]
+    #[Assert\Length(4)]
     private $zipCode;
 
     /**