diff --git a/src/opnsense/mvc/app/models/OPNsense/CaptivePortal/CaptivePortal.xml b/src/opnsense/mvc/app/models/OPNsense/CaptivePortal/CaptivePortal.xml
index 86492aead..4db0a2d6a 100644
--- a/src/opnsense/mvc/app/models/OPNsense/CaptivePortal/CaptivePortal.xml
+++ b/src/opnsense/mvc/app/models/OPNsense/CaptivePortal/CaptivePortal.xml
@@ -65,7 +65,7 @@
                 <allowedMACAddresses type="CSVListField">
                     <Required>N</Required>
                     <ChangeCase>lower</ChangeCase>
-                    <mask>/^([0-9a-fA-F:,])*/u</mask>
+                    <mask>/^((([0-9a-fA-F]{2}:){5}([0-9a-fA-F]{2})([,]){0,1}))*/u</mask>
                     <ValidationMessage>Please enter valid mac addresses</ValidationMessage>
                 </allowedMACAddresses>
                 <template type="ModelRelationField">