diff --git a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/IPAddressWithMask.java b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/IPAddressWithMask.java
index ada2d38..f9eefc1 100644
--- a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/IPAddressWithMask.java
+++ b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/IPAddressWithMask.java
@@ -10,6 +10,10 @@
     public abstract IPVersion getIpVersion();
 
     public IPAddress<?> getSubnetBroadcastAddress() {
+        if (!mask.isCidrMask()) {
+            throw new IllegalArgumentException("Mask Invalid " + mask +
+                                               " cannot get subnet for non CIDR mask");
+        }
         return value.or(mask.not());
     }