diff --git a/docs/modules.rst b/docs/modules.rst
index 49e509b..5b9b075 100644
--- a/docs/modules.rst
+++ b/docs/modules.rst
@@ -1380,6 +1380,9 @@ Parameters:
         * system.lock: specify a command for locking the screen (defaults to 'i3exit lock')
         * system.suspend: specify a command for suspending (defaults to 'i3exit suspend')
         * system.hibernate: specify a command for hibernating (defaults to 'i3exit hibernate')
+        
+Requirements:
+        tkinter (python3-tk package on debian based systems either you can install it as python package)
 
 contributed by `bbernhard <https://github.com/bbernhard>`_ - many thanks!