diff --git a/doc/user/userpdf.tex b/doc/user/userpdf.tex
index cc02cd307f..dda1183688 100644
--- a/doc/user/userpdf.tex
+++ b/doc/user/userpdf.tex
@@ -1,5 +1,6 @@
 % $Id$
 \input{top}
+\usepackage{ifpdf}
 
 \newif\ifpdf
 \ifx\pdfoutput\undefined