Doc fix for SF #962633.
diff --git a/Doc/mac/libmacostools.tex b/Doc/mac/libmacostools.tex
index 06ddbc7..556e46f 100644
--- a/Doc/mac/libmacostools.tex
+++ b/Doc/mac/libmacostools.tex
@@ -8,7 +8,9 @@
This module contains some convenience routines for file-manipulation
on the Macintosh. All file parameters can be specified as
-pathnames, \class{FSRef} or \class{FSSpec} objects.
+pathnames, \class{FSRef} or \class{FSSpec} objects. This module
+expects a filesystem which supports forked files, so it should not
+be used on UFS partitions.
The \module{macostools} module defines the following functions: