diff --git a/src/vnet/session/application_interface.h b/src/vnet/session/application_interface.h
index 14db42a..733f5dc 100644
--- a/src/vnet/session/application_interface.h
+++ b/src/vnet/session/application_interface.h
@@ -53,6 +53,9 @@
   /** Notify app that session or transport are about to be removed */
   void (*session_cleanup_callback) (session_t * s, session_cleanup_ntf_t ntf);
 
+  /** Notify app that half open state was cleaned up (optional) */
+  void (*half_open_cleanup_callback) (session_t *s);
+
   /** Notify app that session was reset */
   void (*session_reset_callback) (session_t * s);