diff --git a/include/villas/nodes/zeromq.h b/include/villas/nodes/zeromq.h
index ba6fb3a94..9f80a3cad 100644
--- a/include/villas/nodes/zeromq.h
+++ b/include/villas/nodes/zeromq.h
@@ -54,6 +54,7 @@ struct zeromq {
 
 	struct {
 		void *socket;	/**< ZeroMQ socket. */
+		void *mon_socket;
 		char *endpoint;
 	} subscriber;
 	
diff --git a/lib/nodes/zeromq.c b/lib/nodes/zeromq.c
index 4083d8d57..47a3acf93 100644
--- a/lib/nodes/zeromq.c
+++ b/lib/nodes/zeromq.c
@@ -43,25 +43,25 @@ static int get_monitor_event(void *monitor, int *value, char **address)
 	if (zmq_msg_recv (&msg, monitor, 0) == -1)
 		return -1; /* Interruped, presumably. */
 
-	assert (zmq_msg_more (&msg));
+	assert(zmq_msg_more (&msg));
 
-	uint8_t *data = (uint8_t *) zmq_msg_data (&msg);
+	uint8_t *data = (uint8_t *) zmq_msg_data(&msg);
 	uint16_t event = *(uint16_t *) (data);
 	if (value)
 		*value = *(uint32_t *) (data + 2);
 
 	/* Second frame in message contains event address */
-	zmq_msg_init (&msg);
-	if (zmq_msg_recv (&msg, monitor, 0) == -1)
+	zmq_msg_init(&msg);
+	if (zmq_msg_recv(&msg, monitor, 0) == -1)
 		return -1; /* Interruped, presumably. */
 
-	assert (!zmq_msg_more (&msg));
+	assert(!zmq_msg_more(&msg));
 
 	if (address) {
-		uint8_t *data = (uint8_t *) zmq_msg_data (&msg);
-		size_t size = zmq_msg_size (&msg);
-		*address = (char *) malloc (size + 1);
-		memcpy (*address, data, size);
+		uint8_t *data = (uint8_t *) zmq_msg_data(&msg);
+		size_t size = zmq_msg_size(&msg);
+		*address = (char *) malloc(size + 1);
+		memcpy(*address, data, size);
 		*address [size] = 0;
 	}
 
@@ -233,17 +233,22 @@ int zeromq_start(struct node *n)
 			break;
 	}
 	
+	if (!z->subscriber.socket || !z->publisher.socket) {
+		ret = -1;
+		goto fail;
+	}
+	
 	ret = zmq_setsockopt(z->publisher.socket, ZMQ_IPV6, &z->ipv6, sizeof(z->ipv6));
 	if (ret)
-		return ret;
+		goto fail;
 
 	ret = zmq_setsockopt(z->subscriber.socket, ZMQ_IPV6, &z->ipv6, sizeof(z->ipv6));
 	if (ret)
 		return ret;
 	
 	/* Subscribe to pubsub messages. */
-	if (z->filter && z->pattern == ZEROMQ_PATTERN_PUBSUB) {
-		ret = zmq_setsockopt(z->subscriber.socket, ZMQ_SUBSCRIBE, z->filter, strlen(z->filter));
+	if (z->pattern == ZEROMQ_PATTERN_PUBSUB) {
+		ret = zmq_setsockopt(z->subscriber.socket, ZMQ_SUBSCRIBE, z->filter, z->filter ? strlen(z->filter) : 0);
 		if (ret < 0)
 			return ret;
 	}
@@ -252,50 +257,55 @@ int zeromq_start(struct node *n)
 		/* Publisher has server role */
 		ret = zmq_setsockopt(z->publisher.socket, ZMQ_CURVE_SECRETKEY, z->curve.server.secret_key, 41);
 		if (ret)
-			return ret;
+			goto fail;
 		
 		ret = zmq_setsockopt(z->publisher.socket, ZMQ_CURVE_PUBLICKEY, z->curve.server.public_key, 41);
 		if (ret)
-			return ret;
+			goto fail;
  
 		int curve_server = 1;
 		ret = zmq_setsockopt(z->publisher.socket, ZMQ_CURVE_SERVER, &curve_server, sizeof(curve_server));
 		if (ret)
-			return ret;
+			goto fail;
 	}
 	
 	if (z->curve.enabled) {
 		/* Create temporary client keys first */
 		ret = zmq_curve_keypair(z->curve.client.public_key, z->curve.client.secret_key);
 		if (ret)
-			return ret;
+			goto fail;
 
 		/* Subscriber has client role */
 		ret = zmq_setsockopt(z->subscriber.socket, ZMQ_CURVE_SECRETKEY, z->curve.client.secret_key, 41);
 		if (ret)
-			return ret;
+			goto fail;
 
 		ret = zmq_setsockopt(z->subscriber.socket, ZMQ_CURVE_PUBLICKEY, z->curve.client.public_key, 41);
 		if (ret)
-			return ret;
+			goto fail;
 
 		ret = zmq_setsockopt(z->subscriber.socket, ZMQ_CURVE_SERVERKEY, z->curve.server.public_key, 41);
 		if (ret)
-			return ret;
+			goto fail;
 	}
 	
 #ifdef ZMQ_BUILD_DRAFT_API
 	/* Monitor handshake events on the server */
 	ret = zmq_socket_monitor(z->subscriber.socket, "inproc://monitor-server", ZMQ_EVENT_HANDSHAKE_SUCCEED | ZMQ_EVENT_HANDSHAKE_FAILED);
-	assert(ret == 0);
+	if (ret < 0)
+		goto fail;
 
 	/* Create socket for collecting monitor events */
-	void *server_mon = zmq_socket(context, ZMQ_PAIR);
-	assert(server_mon);
+	z->subscriber.mon_socket = zmq_socket(context, ZMQ_PAIR);
+	if (!z->subscriber.mon_socket) {
+		ret = -1;
+		goto fail;
+	}
 
 	/* Connect it to the inproc endpoints so they'll get events */
-	ret = zmq_connect(server_mon, "inproc://monitor-server");
-	assert(ret == 0);
+	ret = zmq_connect(z->subscriber.mon_socket, "inproc://monitor-server");
+	if (ret < 0)
+		goto fail;
 #endif
 	
 	/* Bind subscriber socket */
@@ -312,18 +322,21 @@ int zeromq_start(struct node *n)
 		char *ep = list_at(&z->publisher.endpoints, i);
 		
 		ret = zmq_connect(z->publisher.socket, ep);
-		if (ret) {
-			info("Failed to connect to ZeroMQ endpoint: endpoint=%s, error=%s", ep, zmq_strerror(errno));
-			return ret;
-		}
+		if (ret)
+			goto fail;
 	}
 	
 #ifdef ZMQ_BUILD_DRAFT_API
-	ret = get_monitor_event(server_mon, NULL, NULL);
+	ret = get_monitor_event(z->subscriber.mon_socket, NULL, NULL);
 	return ret == ZMQ_EVENT_HANDSHAKE_SUCCEED;
 #else
 	return 0;
 #endif
+	
+fail:
+	info("Failed to start ZeroMQ node: %s, error=%s", node_name(n), zmq_strerror(errno));
+	
+	return ret;
 }
 
 int zeromq_stop(struct node *n)