diff --git a/docs/building.sgml b/docs/building.sgml
index 038c29715d3d777bf3bd3bccbbcbf53d3e7304da..b7c3fbba51677781543db64d96ffe004b69e38e7 100644
--- a/docs/building.sgml
+++ b/docs/building.sgml
@@ -650,7 +650,7 @@ URL="http://sourceware.cygnus.com/docbook-tools/">Cygnus DocBook
 tools</ULink>, which is the most shrink-wrapped SGML suite that we
 could find.  Unfortunately, it's only packaged as RPMs. You can use it
 to generate HTML, DVI (and hence PDF and Postscript) and RTF from any
-DocBook source file (including this manual).
+DocBook source file (including this manual). N.B. The <Emphasis>Cygnus</Emphasis> version of the tools is assumed. Others, such as the SuSE version, may not work.
 </Para>
 </ListItem></VarListEntry>
 <VarListEntry>