diff --git a/src/waterfall.c b/src/waterfall.c
index 1696d18..b37c3c4 100644
--- a/src/waterfall.c
+++ b/src/waterfall.c
@@ -77,6 +77,7 @@ lv_obj_t * waterfall_init(lv_obj_t * parent, uint64_t cur_freq) {
     lv_style_set_line_width(&middle_line_style, 1);
     lv_style_set_line_color(&middle_line_style, lv_color_hex(0xAAAAAA));
     lv_style_set_line_opa(&middle_line_style, LV_OPA_60);
+    lv_style_set_blend_mode(&middle_line_style, LV_BLEND_MODE_ADDITIVE);
 
     lv_msg_subscribe(MSG_SPECTRUM_ZOOM_CHANGED, zoom_changed_cd, NULL);
 
@@ -291,5 +292,5 @@ static void refresh_waterfall( void * arg) {
 
 static void zoom_changed_cd(void * s, lv_msg_t * m) {
     zoom = *(uint16_t *) lv_msg_get_payload(m);
-    lv_style_set_line_width(&middle_line_style, zoom / 2 + 1);
+    lv_style_set_line_width(&middle_line_style, zoom / 2 + 2);
 }