diff --git a/examples/twoway/introspecting.c b/examples/twoway/introspecting.c
index dee04cab049192b77fa40425d612e079e21b1b69..85c29191bf05583c66b6b5b71a80b06f7dcb4faf 100644
--- a/examples/twoway/introspecting.c
+++ b/examples/twoway/introspecting.c
@@ -33,6 +33,7 @@ struct introspecting_private {
   int encoder_initialized;
   struct labcomm_decoder *decoder;
   int decoder_initialized;
+  struct labcomm_lock *lock;
   struct labcomm_reader_action_context reader_action_context;
   struct labcomm_writer_action_context writer_action_context;
   LABCOMM_SIGNATURE_ARRAY_DEF(introspection,