diff --git a/src/libmsc/gsm_04_11_gsup.c b/src/libmsc/gsm_04_11_gsup.c
index 6225c6c..d1c2f27 100644
--- a/src/libmsc/gsm_04_11_gsup.c
+++ b/src/libmsc/gsm_04_11_gsup.c
@@ -201,6 +201,7 @@
 	/* Ensure routing through OsmoHLR to the MT-sending SMSC */
 	gsup_msg.destination_name = trans->sms.gsup_source_name;
 	gsup_msg.destination_name_len = trans->sms.gsup_source_name_len;
+	gsup_client_mux_tx_set_source(trans->net->gcm, &gsup_msg);
 
 	return gsup_client_mux_tx(trans->net->gcm, &gsup_msg);
 }
@@ -222,6 +223,7 @@
 	/* Ensure routing through OsmoHLR to the MT-sending SMSC */
 	gsup_msg.destination_name = trans->sms.gsup_source_name;
 	gsup_msg.destination_name_len = trans->sms.gsup_source_name_len;
+	gsup_client_mux_tx_set_source(trans->net->gcm, &gsup_msg);
 
 	/* SM-RP-Cause value */
 	gsup_msg.sm_rp_cause = &cause;