diff --git a/libmdp/src/engine.c b/libmdp/src/engine.c
index 15b86b4..5f98836 100644
--- a/libmdp/src/engine.c
+++ b/libmdp/src/engine.c
@@ -76,7 +76,7 @@ s_engine_new (char *broker, char *service, int verbose)
     engine_t *self = (engine_t *) zmalloc (sizeof *self);
 
     //  Initialize engine state
-    self->worker = mdp_worker_new (broker, service, verbose);
+    self->worker = mdp_worker_new (NULL, broker, service, verbose);
     self->sell_orders = zlist_new ();
     self->buy_orders = zlist_new ();
     return self;
diff --git a/libmdp/src/test_worker.c b/libmdp/src/test_worker.c
index 78da3cc..07f6ce5 100644
--- a/libmdp/src/test_worker.c
+++ b/libmdp/src/test_worker.c
@@ -7,7 +7,7 @@ int main (int argc, char *argv [])
 {
     int verbose = (argc > 1 && streq (argv [1], "-v"));
     mdp_worker_t *session = mdp_worker_new (
-        "tcp://localhost:5555", "echo", verbose);
+        NULL, "tcp://localhost:5555", "echo", verbose);
 
     while (1) {
         zframe_t *reply_to;