diff --git a/java_gen/templates/_imports.java b/java_gen/templates/_imports.java
index 50ba198..bac7065 100644
--- a/java_gen/templates/_imports.java
+++ b/java_gen/templates/_imports.java
@@ -13,3 +13,4 @@
 import org.openflow.exceptions.*;
 import org.jboss.netty.buffer.ChannelBuffer;
 import org.jboss.netty.buffer.ChannelBuffers;
+import com.google.common.collect.ImmutableList;
diff --git a/java_gen/templates/of_class.java b/java_gen/templates/of_class.java
index 18dae2b..eae75ba 100644
--- a/java_gen/templates/of_class.java
+++ b/java_gen/templates/of_class.java
@@ -155,7 +155,7 @@
     final static Writer WRITER = new Writer();
     static class Writer implements OFMessageWriter<${impl_class}> {
         @Override
-        public int write(ChannelBuffer bb, ${impl_class} message) {
+        public void write(ChannelBuffer bb, ${impl_class} message) {
 //:: if not msg.is_fixed_length:
             int startIndex = bb.writerIndex();
 //:: #end
diff --git a/java_gen/templates/of_interface.java b/java_gen/templates/of_interface.java
index b969d50..186b787 100644
--- a/java_gen/templates/of_interface.java
+++ b/java_gen/templates/of_interface.java
@@ -35,7 +35,7 @@
 
 //:: include("_imports.java", msg=msg)
 
-public interface ${msg.name} ${"extends %s" % msg.parent_interface if msg.parent_interface else ""} {
+public interface ${msg.name} extends OFObject${", %s" % msg.parent_interface if msg.parent_interface else ""}{
 //:: for prop in msg.members:
     ${prop.java_type.public_type} get${prop.title_name}()${ "" if prop.is_universal else " throws UnsupportedOperationException"};
 //:: #endfor