diff --git a/src/libmsc/gsup_client_mux.c b/src/libmsc/gsup_client_mux.c
index 7ec1712..292c2a9 100644
--- a/src/libmsc/gsup_client_mux.c
+++ b/src/libmsc/gsup_client_mux.c
@@ -150,13 +150,13 @@
 	if (!OSMO_GSUP_IS_MSGT_REQUEST(gsup_orig->message_type))
 		return;
 
-	OSMO_STRLCPY_ARRAY(gsup_reply.imsi, gsup_orig->imsi);
-
 	gsup_reply = (struct osmo_gsup_message){
 		.cause = cause,
 		.message_type = OSMO_GSUP_TO_MSGT_ERROR(gsup_orig->message_type),
 	};
 
+	OSMO_STRLCPY_ARRAY(gsup_reply.imsi, gsup_orig->imsi);
+
 	if (osmo_gsup_client_enc_send(gcm->gsup_client, &gsup_reply))
 		LOGP(DLGSUP, LOGL_ERROR, "Failed to send Error reply (imsi=%s)\n",
 		     osmo_quote_str(gsup_orig->imsi, -1));