strip mISDN hardware header before putting B-channel data into subchannel demuxer

diff --git a/src/e1_input.c b/src/e1_input.c
index 813ec97..cd23115 100644
--- a/src/e1_input.c
+++ b/src/e1_input.c
@@ -373,7 +373,7 @@
 		}
 		break;
 	case E1INP_TS_TYPE_TRAU:
-		ret = subch_demux_in(&ts->trau.demux, msg->data, msg->len);
+		ret = subch_demux_in(&ts->trau.demux, msg->l2h, msgb_l2len(msg));
 		break;
 	default:
 		ret = -EINVAL;