It is important that whitespace is not allowed in directive "SSIStartTag" and "SSIEndTag". However, none of these two directive mentioned about this tips. I think it is better to add "SSIStartTag/SSIEndTag may not contain any whitespaces" in the doc http://httpd.apache.org/docs/2.4/mod/mod_include.html#ssistarttag and http://httpd.apache.org/docs/2.4/mod/mod_include.html#ssiendtag .