diff --git a/runtime/doc/windows.txt b/runtime/doc/windows.txt
index 87a5d6f..fa94896 100644
--- a/runtime/doc/windows.txt
+++ b/runtime/doc/windows.txt
@@ -1,4 +1,4 @@
-*windows.txt*   For Vim version 8.1.  Last change: 2019 Jul 27
+*windows.txt*   For Vim version 8.1.  Last change: 2019 Aug 04
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -874,7 +874,16 @@
 	width		maximum width of the popup
 Example: >
 	:set previewpopup=height:10,width:60
-<
+
+A few peculiarities:
+- If the file is in a buffer already, it will be re-used.  This will allow for
+  editing the file while it's visible in the popup window.
+- No ATTENTION dialog will be used, since you can't edit the file in the popup
+  window.  However, if you later open the same buffer in a normal window, you
+  may not notice it's edited elsewhere.  And when then using ":edit" to
+  trigger the ATTENTION and responding "A" for Abort, the preview window will
+  become empty.
+
 						*:pta* *:ptag*
 :pta[g][!] [tagname]
 		Does ":tag[!] [tagname]" and shows the found tag in a