diff --git a/daemon/codec.c b/daemon/codec.c
index 331a5fbaf..eee4b7635 100644
--- a/daemon/codec.c
+++ b/daemon/codec.c
@@ -2652,6 +2652,7 @@ static void __dtx_send_later(struct timerthread_queue *ttq, void *p) {
 	}
 
 	int ptime = dtxb->ptime;
+	time_t dtxb_start = dtxb->start;
 
 	mutex_unlock(&dtxb->lock);
 
@@ -2673,7 +2674,7 @@ static void __dtx_send_later(struct timerthread_queue *ttq, void *p) {
 					"Decoder error while processing buffered RTP packet");
 	}
 	else {
-		unsigned int diff = rtpe_now.tv_sec - dtxb->start;
+		int diff = rtpe_now.tv_sec - dtxb_start;
 
 		if (rtpe_config.max_dtx <= 0 || diff < rtpe_config.max_dtx) {
 			ilogs(dtx, LOG_DEBUG, "RTP media for TS %lu missing, triggering DTX", ts);