diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index 78f63fc..2fb6a85 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -245,7 +245,7 @@
 	/* Note: this might fail if not CAP_NET_RAW */
 	if (listener->interface) {
 		if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE,
-			       listener->interface, strlen(listener->interface)) == -1) {
+			       listener->interface, strlen(listener->interface) + 1) == -1) {
 			msg = "cannot bind listener to device";
 			err |= ERR_WARN;
 		}