diff --git a/booklet.sh b/booklet.sh
index cda8981..11d74c8 100644
--- a/booklet.sh
+++ b/booklet.sh
@@ -34,11 +34,12 @@ rm booklet-stylesheet.css.tmp
 
 # Turn the HTML page into a PDF with weasyprint
 # ---------------------------------------------------------------
-echo ">>> generating $WIKIPAGE.pdf (with weasyprint)"
-weasyprint https://pzwiki.wdka.nl/mediadesign/$WIKIPAGE?action=render --stylesheet booklet-stylesheet.css $WIKIPAGE.pdf
+PDFNAME=$(echo "$WIKIPAGE" | tr :/#%{}\&\\\<\>*?/\!\'\"@+\`= _)
+echo ">>> generating $PDFNAME.pdf (with weasyprint)"
+weasyprint https://pzwiki.wdka.nl/mediadesign/$WIKIPAGE?action=render --stylesheet booklet-stylesheet.css $PDFNAME.pdf
 
 # And turn the PDF into an A5 booklet PDF for printing
 # ---------------------------------------------------------------
 # pdfbook2 is part of the texlive-extra-utils package in Debian
-echo ">>> generating $WIKIPAGE-book.pdf (with pdfbook2)"
-pdfbook2 --paper=a4paper --short-edge --no-crop $WIKIPAGE.pdf
+echo ">>> generating $PDFNAME-book.pdf (with pdfbook2)"
+pdfbook2 --paper=a4paper --short-edge --no-crop $PDFNAME.pdf