diff --git a/channels/chan_zap.c b/channels/chan_zap.c
index 0303be1313..919a9ab195 100755
--- a/channels/chan_zap.c
+++ b/channels/chan_zap.c
@@ -6965,7 +6965,7 @@ static void *pri_dchannel(void *vpri)
 				} else {
 					chanpos = pri_fixup_principle(pri, chanpos, e->ring.call);
 					if (chanpos > -1) {
-						ast_mutex_lock(&pri->pvts[x]->lock);
+						ast_mutex_lock(&pri->pvts[chanpos]->lock);
 						/* queue DTMF frame if the PBX for this call was already started (we're forwarding INFORMATION further on */
 						if (pri->overlapdial && pri->pvts[chanpos]->call==e->ring.call && pri->pvts[chanpos]->owner) {
 							/* how to do that */
@@ -6980,7 +6980,7 @@ static void *pri_dchannel(void *vpri)
 								}
 							}
 						}
-						ast_mutex_unlock(&pri->pvts[x]->lock);
+						ast_mutex_unlock(&pri->pvts[chanpos]->lock);
 					}
 				}
 				break;