diff --git a/sk.c b/sk.c
index 9c98c1d..f18b2bf 100644
--- a/sk.c
+++ b/sk.c
@@ -395,7 +395,7 @@ int sk_set_priority(int fd, uint8_t dscp)
 int sk_timestamping_init(int fd, const char *device, enum timestamp_type type,
 			 enum transport_type transport)
 {
-	int err, filter1, filter2 = 0, flags, tx_type;
+	int err, filter1, filter2 = 0, flags, tx_type = HWTSTAMP_TX_ON;
 
 	switch (type) {
 	case TS_SOFTWARE: