diff --git a/kitty/cell_vertex.glsl b/kitty/cell_vertex.glsl
index 4140eb5de..b7c9ecc42 100644
--- a/kitty/cell_vertex.glsl
+++ b/kitty/cell_vertex.glsl
@@ -159,7 +159,7 @@ void main() {
     int mark = int(text_attrs >> MARK_SHIFT) & MARK_MASK;
     uint has_mark = uint(step(1, float(mark)));
     uint bg_as_uint = resolve_color(colors[bg_index], default_colors[bg_index]);
-    bg_as_uint = has_mark * color_table[NUM_COLORS + mark] + (ONE - has_mark) * bg_as_uint;
+    bg_as_uint = has_mark * color_table[NUM_COLORS + mark - 1] + (ONE - has_mark) * bg_as_uint;
     vec3 bg = color_to_vec(bg_as_uint);
     uint fg_as_uint = resolve_color(colors[fg_index], default_colors[fg_index]);
     // }}}
@@ -169,7 +169,7 @@ void main() {
 
 
     // Foreground
-    fg_as_uint = has_mark * color_table[NUM_COLORS + MARK_MASK + 1 + mark] + (ONE - has_mark) * fg_as_uint;
+    fg_as_uint = has_mark * color_table[NUM_COLORS + MARK_MASK + mark] + (ONE - has_mark) * fg_as_uint;
     foreground = color_to_vec(fg_as_uint);
     float has_dim = float((text_attrs >> DIM_SHIFT) & ONE);
     effective_text_alpha = inactive_text_alpha * mix(1.0, dim_opacity, has_dim);