diff --git a/doc/tint2.md b/doc/tint2.md
index 3024b14..b88a3d4 100644
--- a/doc/tint2.md
+++ b/doc/tint2.md
@@ -413,9 +413,9 @@ The following options configure the task buttons in the taskbar:
 
   * `task_tooltip = boolean (0 or 1)` : Whether to show tooltips for tasks.
 
-  * `task_thumbnail = boolean (0 or 1)` : Whether to show thumbnail tooltips for tasks.
+  * `task_thumbnail = boolean (0 or 1)` : Whether to show thumbnail tooltips for tasks. *(since 16.0)*
 
-  * `task_thumbnail_size = width` : Thumbnail size.
+  * `task_thumbnail_size = width` : Thumbnail size. *(since 16.0)*
 
   * `task_maximum_size = width height`
     * `width` is used with horizontal panels to limit the size of the tasks. Use `width = 0` to get full taskbar width.