diff --git a/software/obsolete/osmo_e1f.c b/software/obsolete/osmo_e1f.c
index 6a8725c..cbcd0db 100644
--- a/software/obsolete/osmo_e1f.c
+++ b/software/obsolete/osmo_e1f.c
@@ -206,7 +206,7 @@
 /* pull a single to-be-transmitted byte for TS0 */
 static uint8_t e1_pull_ts0(struct osmo_e1f_instance *e1i)
 {
-	uint8_t ret;
+	uint8_t ret = 0;
 
 	/* according to Table 5B/G.704 - CRC-4 multiframe structure */
 	if ((e1i->tx.frame_nr % 2) == 0) {