diff --git a/html-src/gen-html.py b/html-src/gen-html.py
index bb009eb7..ada3da03 100755
--- a/html-src/gen-html.py
+++ b/html-src/gen-html.py
@@ -89,7 +89,7 @@ main_footer = '''
 rules_header = '''<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
 <html>
 <head>
-<title>%s</title>
+<title>%(title)s</title>
 <meta name="license" content="GNU General Public License">
 <meta http-equiv="content-type" content="text/html; charset=utf-8">
 </head>
@@ -238,7 +238,7 @@ def gen_rules_html():
         outfile = open(
             os.path.join('html', 'rules', filename), 'w', encoding='utf-8')
         if dir == 'rules':
-            print(rules_header % title, file=outfile)
+            print(rules_header % {'title': title}, file=outfile)
         else:  # d == 'wikipedia'
             print(wikipedia_header % title, file=outfile)
         with open(os.path.join(dir, filename), 'r', encoding='utf-8') as file:
