diff --git a/docs/content/ui/getting-started/upgrade/1-6.mdx b/docs/content/ui/getting-started/upgrade/1-6.mdx
index 5e142597a..8d7099105 100644
--- a/docs/content/ui/getting-started/upgrade/1-6.mdx
+++ b/docs/content/ui/getting-started/upgrade/1-6.mdx
@@ -362,6 +362,7 @@ Variable|What to use instead
 `$form-switch-bg-image`, `$form-switch-bg-image-dark`, `$form-switch-checked-bg-image`, `$form-switch-checked-bg-position`, `$form-switch-focus-bg-image`, `$form-switch-color-dark`|See [Masked icons](#masked-icons). No effect any more.
 `$form-check-input-checked-bg-image-dark`|See [Masked icons](#masked-icons). No effect any more.
 `$navbar-light-toggler-icon-bg`, `$navbar-dark-toggler-icon-bg`|`$navbar-toggler-icon-bg`. No effect any more.
+`$lighten-dark`|`$active-bg`, which is a `light-dark()` value and carries its own dark color, so `--tblr-active-bg` no longer reads it. Hover backgrounds use the new `$hover-bg` and `--tblr-hover-bg`. No effect any more.
 `$input-btn-focus-width`|`$focus-ring-width`. A changed value still sets the ring width.
 `$input-btn-focus-color`|`$focus-ring-color`. A changed value still sets the ring color.
 `$btn-focus-box-shadow`, `$btn-close-focus-shadow`, `$pagination-focus-box-shadow`, `$accordion-btn-focus-box-shadow`|The ring variables. A changed value is still drawn as a shadow, next to the outline.