diff --git a/src/osmo-bsc/abis_rsl.c b/src/osmo-bsc/abis_rsl.c
index ac8006d33..7525e310c 100644
--- a/src/osmo-bsc/abis_rsl.c
+++ b/src/osmo-bsc/abis_rsl.c
@@ -939,11 +939,7 @@ int rsl_siemens_mrpci(struct gsm_lchan *lchan, struct rsl_mrpci *mrpci)
 /* Chapter 8.3.1 */
 int rsl_data_request(struct msgb *msg, uint8_t link_id)
 {
-	int chan_nr = gsm_lchan2chan_nr(msg->lchan, true);
-	if (chan_nr < 0) {
-		msgb_free(msg);
-		return chan_nr;
-	}
+	int chan_nr;
 
 	if (msg->lchan == NULL) {
 		LOGP(DRSL, LOGL_ERROR, "cannot send DATA REQUEST to unknown lchan\n");
@@ -951,6 +947,12 @@ int rsl_data_request(struct msgb *msg, uint8_t link_id)
 		return -EINVAL;
 	}
 
+	chan_nr = gsm_lchan2chan_nr(msg->lchan, true);
+	if (chan_nr < 0) {
+		msgb_free(msg);
+		return chan_nr;
+	}
+
 	rsl_rll_push_l3(msg, RSL_MT_DATA_REQ, chan_nr, link_id, 1);
 
 	msg->dst = rsl_chan_link(msg->lchan);