diff --git a/pywb/rewrite/html_rewriter.py b/pywb/rewrite/html_rewriter.py
index 21989a29..e174c208 100644
--- a/pywb/rewrite/html_rewriter.py
+++ b/pywb/rewrite/html_rewriter.py
@@ -220,7 +220,7 @@ class HTMLRewriterMixin(object):
 
         values = value.split(',')
         values = [self._rewrite_url(v.strip()) for v in values]
-        return ', '.join(values)
+        return ','.join(values)
 
     def _rewrite_css(self, css_content):
         if css_content: