diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4c3ad3e4..19f5c7ad 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -56,6 +56,9 @@
   unrelated cells (https://codeberg.org/dnkl/foot/issues/816).
 * OSC-8 URIs incorrectly being dropped when resizing the terminal
   window with the alternate screen active.
+* CSD border not being dimmed when window is not focused.
+* Visual corruption with large CSD borders
+  (https://codeberg.org/dnkl/foot/issues/823).
 
 
 ### Security
diff --git a/render.c b/render.c
index 2710c0a2..cd38d712 100644
--- a/render.c
+++ b/render.c
@@ -1763,14 +1763,16 @@ render_csd_border(struct terminal *term, enum csd_surface surf_idx,
      * The “visible” border.
      */
 
-    int bwidth = term->conf->csd.border_width;          /* Full border size */
-    int vwidth = term->conf->csd.border_width_visible;  /* Visibls size */
+    int bwidth = max(term->conf->csd.border_width,
+                     term->conf->csd.border_width_visible); /* Full border size */
+    int vwidth = term->conf->csd.border_width_visible;      /* Visibls size */
 
     if (vwidth > 0) {
 
         const struct config *conf = term->conf;
         int x = 0, y = 0, w = 0, h = 0;
 
+
         switch (surf_idx) {
         case CSD_SURF_TOP:
         case CSD_SURF_BOTTOM:
@@ -1788,17 +1790,33 @@ render_csd_border(struct terminal *term, enum csd_surface surf_idx,
             h = info->height;
             break;
 
-        default:
-            break;
+        case CSD_SURF_TITLE:
+        case CSD_SURF_MINIMIZE:
+        case CSD_SURF_MAXIMIZE:
+        case CSD_SURF_CLOSE:
+        case CSD_SURF_COUNT:
+            BUG("unexpected CSD surface type");
         }
 
+        xassert(x >= 0);
+        xassert(y >= 0);
+        xassert(w >= 0);
+        xassert(h >= 0);
+
+        xassert(x + w <= info->width);
+        xassert(y + h <= info->height);
+
         uint32_t _color =
             conf->csd.color.border_set ? conf->csd.color.border :
             conf->csd.color.title_set ? conf->csd.color.title :
             0xffu << 24 | term->conf->colors.fg;
+        if (!term->visual_focus)
+            _color = color_dim(term, _color);
+
         uint16_t alpha = _color >> 24 | (_color >> 24 << 8);
         pixman_color_t color = color_hex_to_pixman_with_alpha(_color, alpha);
 
+
         pixman_image_fill_rectangles(
             PIXMAN_OP_SRC, buf->pix[0], &color, 1,
             &(pixman_rectangle16_t){x, y, w, h});