diff --git a/forms/set_port_out_pin.rb b/forms/set_port_out_pin.rb
index b7ed6d872355de17f983f9c42e7c9af8853bad32..2550bb6f785473262e567371e30dd9138ae70f14 100644
--- a/forms/set_port_out_pin.rb
+++ b/forms/set_port_out_pin.rb
@@ -10,7 +10,8 @@ field(
 	type: "text-private",
 	label: "Port-out PIN",
 	required: true,
-	description: "Enter 4-10 alphanumeric characters"
+	description: "Enter 4-10 alphanumeric characters",
+	regex: /\A[\w\d]{4,10}\Z/
 )
 
 field(
@@ -18,5 +19,6 @@ field(
 	type: "text-private",
 	label: "Confirm PIN",
 	required: true,
-	description: "Re-enter the same PIN to confirm"
+	description: "Re-enter the same PIN to confirm",
+	regex: /\A[\w\d]{4,10}\Z/
 )