diff --git a/doc/lispref/os.texi b/doc/lispref/os.texi
index e3dcd6c778..5323f5f9a1 100644
--- a/doc/lispref/os.texi
+++ b/doc/lispref/os.texi
@@ -3232,6 +3232,10 @@ File Notifications

 @deffn Command file-notify-rm-all-watches
 Removes all existing file notification watches from Emacs.
+
+Use this command with caution, because it could have unexpected side
+effects on packages relying on file watches.  It is intended mainly
+for debugging purposes, or when Emacs has been stalled.
 @end deffn

 @defun file-notify-valid-p descriptor