diff --git a/tools/pdf2html.cgi b/tools/pdf2html.cgi
index 4ddba6dc..13001c5f 100755
--- a/tools/pdf2html.cgi
+++ b/tools/pdf2html.cgi
@@ -32,7 +32,7 @@ def q(x):
     return x.replace('&','&amp;').replace('>','&gt;').replace('<','&lt;').replace('"','&quot;')
 
 # encode parameters as a URL
-Q = re.compile(r'[^a-zA-Z0-9_.-=]')
+Q = re.compile(r'[^a-zA-Z0-9_.\-=]')
 def url(base, **kw):
     r = []
     for (k,v) in kw.iteritems():