diff --git a/include/osmocom/core/msgb.h b/include/osmocom/core/msgb.h
index 08dfaac..915c4a0 100644
--- a/include/osmocom/core/msgb.h
+++ b/include/osmocom/core/msgb.h
@@ -29,12 +29,13 @@
 struct msgb {
 	struct llist_head list;
 
-	/* routing information. */
-	void *dst;
 
 	/* Part of which TRX logical channel we were received / transmitted */
 	/* FIXME: move them into the control buffer */
-	struct gsm_bts_trx *trx;
+	union {
+		void *dst;
+		struct gsm_bts_trx *trx;
+	};
 	struct gsm_lchan *lchan;
 
 	/* the Layer1 header (if any) */