diff --git a/kitty/border_vertex.glsl b/kitty/border_vertex.glsl
index 4a74b50b2..4d9647c03 100644
--- a/kitty/border_vertex.glsl
+++ b/kitty/border_vertex.glsl
@@ -42,7 +42,11 @@ void main() {
     float is_window_bg = is_integer_value(rc, 3.);
     float is_default_bg = is_integer_value(rc, 0.);
     color3 = is_window_bg * window_bg + (1. - is_window_bg) * color3;
+    // Border must be always drawn opaque
+    float is_border_bg = 1. - step(0.5, abs((float(rc) - 2.) * (float(rc) - 1.))); // 1 if rc in (1, 2) else 0
     float final_opacity = is_default_bg * tint_opacity + (1. - is_default_bg) * background_opacity;
+    final_opacity = is_border_bg + (1. - is_border_bg) * final_opacity;
     float final_premult_opacity = is_default_bg * tint_premult + (1. - is_default_bg) * background_opacity;
+    final_premult_opacity = is_border_bg + (1. - is_border_bg) * final_premult_opacity;
     color = vec4(color3 * final_premult_opacity, final_opacity);
 }