diff --git a/lib/tpl/dokuwiki/images/pagetools-build.php b/lib/tpl/dokuwiki/images/pagetools-build.php
index 3cf35b2eae..eaceeb2573 100644
--- a/lib/tpl/dokuwiki/images/pagetools-build.php
+++ b/lib/tpl/dokuwiki/images/pagetools-build.php
@@ -15,6 +15,8 @@
 $GAMMA = 0.8;
 $OPTIPNG = '/usr/bin/optipng';
 
+if('cli' != php_sapi_name()) die('please run from commandline');
+
 // load input images
 $input = glob('pagetools/*.png');
 sort($input);