diff --git a/src/libcharon/plugins/forecast/forecast_listener.c b/src/libcharon/plugins/forecast/forecast_listener.c
index 3d000bc48..b70945717 100644
--- a/src/libcharon/plugins/forecast/forecast_listener.c
+++ b/src/libcharon/plugins/forecast/forecast_listener.c
@@ -122,7 +122,7 @@ static bool ts2in(traffic_selector_t *ts,
 	{
 		memcpy(&addr->s_addr, net->get_address(net).ptr, 4);
 		net->destroy(net);
-		mask->s_addr = htonl(0xffffffffU << (32 - bits));
+		mask->s_addr = bits ? htonl(0xffffffffU << (32 - bits)) : 0;
 		return TRUE;
 	}
 	return FALSE;