diff --git a/lib/font_renderer/font_renderer.cpp b/lib/font_renderer/font_renderer.cpp
index d0107711..4d236269 100644
--- a/lib/font_renderer/font_renderer.cpp
+++ b/lib/font_renderer/font_renderer.cpp
@@ -208,6 +208,9 @@ int FontRendererBakeFontBitmap(FontRenderer *font_renderer, int font_height,
         glyph_info.yoff = -pad_y;
         glyph_info.xadvance = (x_next - x) / subpixel_scale;
 
+#ifdef FONT_RENDERER_DEBUG
+        glyph_info.ybaseline = pixels_height - 1 - y_baseline;
+#endif
         if (glyph_info.x1 > glyph_info.x0) {
             glyph_lut_convolution(ren_buf, lcd_lut, cover_swap_buffer, glyph_info);
         }
diff --git a/lib/font_renderer/font_renderer.h b/lib/font_renderer/font_renderer.h
index 0d03bad9..c0c1fa43 100644
--- a/lib/font_renderer/font_renderer.h
+++ b/lib/font_renderer/font_renderer.h
@@ -11,6 +11,9 @@ extern "C" {
 typedef struct {
   unsigned short x0, y0, x1, y1;
   float xoff, yoff, xadvance;
+#ifdef FONT_RENDERER_DEBUG
+  int ybaseline;
+#endif
 } GlyphBitmapInfo;
 
 struct FontRendererImpl;
diff --git a/src/renderer.c b/src/renderer.c
index 58ea0156..6abb1597 100644
--- a/src/renderer.c
+++ b/src/renderer.c
@@ -152,6 +152,22 @@ void debug_bitmap_draw_rect(RenImage *image, GlyphBitmapInfo *glyph) {
     c[y * w].g = c[y * w].g >> 1;
     c[y * w].b = c[y * w].b >> 1;
   }
+  c = image->pixels + glyph->ybaseline * w;
+  for (int x = x0 * subpixel; x < x1 * subpixel; x++) {
+    c[x].g = c[x].g >> 1;
+    c[x].r = c[x].r >> 1;
+  }
+  const int x_or = x0 - glyph->xoff, y_or = y0 - glyph->yoff;
+  c = image->pixels + y_or * w;
+  for (int x = x_or * subpixel; x < x1 * subpixel; x++) {
+    c[x].b = c[x].b >> 1;
+    c[x].r = c[x].r >> 1;
+  }
+  c = image->pixels + x_or * subpixel;
+  for (int y = y_or; y < y1; y++) {
+    c[y * w].b = c[y * w].b >> 1;
+    c[y * w].r = c[y * w].r >> 1;
+  }
 }
 #endif