diff --git a/daemon/worker.c b/daemon/worker.c
index 759fd0457..85d5b7de0 100644
--- a/daemon/worker.c
+++ b/daemon/worker.c
@@ -1884,7 +1884,7 @@ worker_init(struct worker* worker, struct config_file *cfg,
 #endif
 		) {
 		if(!dt_io_thread_start(dtenv->dtio, comm_base_internal(
-			worker->base))) {
+			worker->base), worker->daemon->num)) {
 			log_err("could not start dnstap io thread");
 			worker_delete(worker);
 			return 0;
diff --git a/dnstap/dtstream.c b/dnstap/dtstream.c
index 8d98c559d..bd4d39acb 100644
--- a/dnstap/dtstream.c
+++ b/dnstap/dtstream.c
@@ -277,7 +277,9 @@ int dt_io_thread_register_queue(struct dt_io_thread* dtio,
 {
 	struct dt_io_list_item* item = malloc(sizeof(*item));
 	if(!item) return 0;
+	lock_basic_lock(&mq->lock);
 	mq->dtio = dtio;
+	lock_basic_unlock(&mq->lock);
 	item->queue = mq;
 	item->next = dtio->io_list;
 	dtio->io_list = item;
@@ -297,7 +299,9 @@ void dt_io_thread_unregister_queue(struct dt_io_thread* dtio,
 			if(prev) prev->next = item->next;
 			else dtio->io_list = item->next;
 			/* the queue itself only registered, not deleted */
+			lock_basic_lock(&item->queue->lock);
 			item->queue->dtio = NULL;
+			lock_basic_unlock(&item->queue->lock);
 			free(item);
 			dtio->io_list_iter = NULL;
 			return;
@@ -1269,6 +1273,7 @@ static void* dnstap_io(void* arg)
 	struct dt_io_thread* dtio = (struct dt_io_thread*)arg;
 	time_t secs = 0;
 	struct timeval now;
+	log_thread_set(&dtio->threadnum);
 
 	/* setup */
 	verbose(VERB_ALGO, "start dnstap io thread");
@@ -1288,7 +1293,8 @@ static void* dnstap_io(void* arg)
 }
 #endif /* THREADS_DISABLED */
 
-int dt_io_thread_start(struct dt_io_thread* dtio, void* event_base_nothr)
+int dt_io_thread_start(struct dt_io_thread* dtio, void* event_base_nothr,
+	int numworkers)
 {
 	/* set up the thread, can fail */
 #ifndef USE_WINSOCK
@@ -1305,6 +1311,7 @@ int dt_io_thread_start(struct dt_io_thread* dtio, void* event_base_nothr)
 #endif
 
 	/* start the thread */
+	dtio->threadnum = numworkers+1;
 	dtio->started = 1;
 #ifndef THREADS_DISABLED
 	ub_thread_create(&dtio->tid, dnstap_io, dtio);
diff --git a/dnstap/dtstream.h b/dnstap/dtstream.h
index c2b898b86..9309f5c0b 100644
--- a/dnstap/dtstream.h
+++ b/dnstap/dtstream.h
@@ -92,6 +92,9 @@ struct dt_msg_entry {
  * IO thread that reads from the queues and writes them.
  */
 struct dt_io_thread {
+	/** the thread number for the dtio thread,
+	 * must be first to cast thread arg to int* in checklock code. */
+	int threadnum;
 	/** event base, for event handling */
 	void* event_base;
 	/** list of queues that is registered to get written */
@@ -348,9 +351,12 @@ void dt_io_thread_unregister_queue(struct dt_io_thread* dtio,
  * @param event_base_nothr: the event base to attach the events to, in case
  * 	we are running without threads.  With threads, this is ignored
  * 	and a thread is started to process the dnstap log messages.
+ * @param numworkers: number of worker threads.  The dnstap io thread is
+ * 	that number +1 as the threadnumber (in logs).
  * @return false on failure.
  */
-int dt_io_thread_start(struct dt_io_thread* dtio, void* event_base_nothr);
+int dt_io_thread_start(struct dt_io_thread* dtio, void* event_base_nothr,
+	int numworkers);
 
 /** 
  * Stop the io thread