diff --git a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/annotations/Immutable.java b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/annotations/Immutable.java
new file mode 100644
index 0000000..5de2171
--- /dev/null
+++ b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/annotations/Immutable.java
@@ -0,0 +1,13 @@
+package org.projectfloodlight.openflow.annotations;
+
+/**
+ * This annotation marks a class that is considered externally immutable. I.e.,
+ * the externally visible state of the class will not change after its
+ * construction. Such a class can be freely shared between threads and does not
+ * require defensive copying (don't call clone).
+ *
+ * @author Andreas Wundsam <andreas.wundsam@bigswitch.com>
+ */
+public @interface Immutable {
+
+}