diff --git a/runtime/doc/windows.txt b/runtime/doc/windows.txt
index 7f5d970..6d9aa0b 100644
--- a/runtime/doc/windows.txt
+++ b/runtime/doc/windows.txt
@@ -986,9 +986,10 @@
 list of buffers. |unlisted-buffer|
 
 
-:files[!]					*:files*
-:buffers[!]					*:buffers* *:ls*
-:ls[!]		Show all buffers.  Example:
+:files[!] [flags]				*:files*
+:buffers[!] [flags]				*:buffers* *:ls*
+:ls[!] [flags]
+		Show all buffers.  Example:
 
 			1 #h   "/test/text"		line 1 ~
 			2u     "asdf"			line 0 ~
@@ -1014,6 +1015,21 @@
 		    +	a modified buffer
 		    x   a buffer with read errors
 
+		[flags] can be a combination of the following characters,
+		which restrict the buffers to be listed:
+		     +   modified buffers
+		     -   buffers with 'modifiable' off
+		     =   readonly buffers
+		     a   active buffers
+		     u   unloaded buffers (overrides the "!")
+		     h   hidden buffers
+		     x   buffers with a read error
+		     %   current buffer
+		     #   alternate buffer
+		Combining flags means they are "and"ed together, e.g.:
+		     h+   hidden buffers which are modified
+		     a+   active buffers which are modified
+
 						*:bad* *:badd*
 :bad[d]	[+lnum] {fname}
 		Add file name {fname} to the buffer list, without loading it.