diff --git a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/IPv6AddressWithMask.java b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/IPv6AddressWithMask.java
index 7259c7f..2e7ff5e 100644
--- a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/IPv6AddressWithMask.java
+++ b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/IPv6AddressWithMask.java
@@ -88,5 +88,14 @@
         }
     }
 
+    @Override
+    public boolean contains(IPAddress<?> ip) {
+        if (string == null) {
+            throw new NullPointerException("String must not be null");
+        }
+        
+        IPv6Address ipv6 = (IPv6Address) ip;
+        return this.matches(ipv6);
+    }
 
 }