diff --git a/src/controller/cluster.c b/src/controller/cluster.c
index 9c9e48e..0e0b15c 100644
--- a/src/controller/cluster.c
+++ b/src/controller/cluster.c
@@ -557,8 +557,9 @@ static int make_heartbeat(cluster_t* c, endpoint_t* ep)
 
 static int check_worker_timeout_(void* arg1, void* arg2)
 {
-    cluster_t*        c = (cluster_t*)arg1;
-    worker_t*         w = (worker_t*)arg2;
+    cluster_t*        c  = (cluster_t*)arg1;
+    worker_t*         w  = (worker_t*)arg2;
+    worker_t*         w1 = NULL;
     endpoint_t*       ep;
     time_t            now = time(NULL);
     int               timeout;
@@ -577,6 +578,12 @@ static int check_worker_timeout_(void* arg1, void* arg2)
         return 0;
     }
 
+    /* grab lock on worker */
+    w1 = obj_ref(w, OBJREF_UPDATE);
+    if (w1 == NULL) {
+        return -EINVAL;
+    }
+    
     config  = c->myconf->cluster_config;
     timeout = config->heartbeat_interval * config->inactive_heartbeat_count;
 
@@ -585,6 +592,7 @@ static int check_worker_timeout_(void* arg1, void* arg2)
               w->host.name);
 
         mark_worker_unavail(c, w);
+        obj_deref(w1);
 
         return 0;
     } else {
@@ -603,11 +611,14 @@ static int check_worker_timeout_(void* arg1, void* arg2)
 
             if (rc < 0) {
                 ERROR("%s make_heartbeat to %s failed", __func__, w->host.name);
+
+                obj_deref(w1);
                 return rc;
             }
         }
     }
 
+    obj_deref(w1);
     return 0;
 }
 
diff --git a/src/controller/worker.c b/src/controller/worker.c
index 1e5e29f..0c21a2f 100644
--- a/src/controller/worker.c
+++ b/src/controller/worker.c
@@ -521,6 +521,8 @@ int handle_worker_leave(cluster_t* c, int idx)
         return -errno;
     }
 
+    w->ep = NULL;
+
     mark_worker_unavail(c, w);
 
     obj_deref(w);