(tooltip-gud-tips-p): Doc fix.

1 files changed, 4 insertions, 1 deletions

diff --git a/lisp/tooltip.el b/lisp/tooltip.el
index 98aae2e041b..92e95fcc750 100644
--- a/lisp/tooltip.el
+++ b/lisp/tooltip.el
@@ -128,7 +128,10 @@ position to pop up the tooltip."
 
 
 (defcustom tooltip-gud-tips-p nil
-  "*Non-nil means show tooltips in GUD sessions."
+  "*Non-nil means show tooltips in GUD sessions.
+Setting this variable directly with `setq' has no effect;
+you should either set it with the Customization facility
+or use the function `tooltip-gud-tips-activate'."
   :type 'boolean
   :tag "GUD"
   :set #'(lambda (symbol on)