diff --git a/packages/templating/plugin/html_scanner.js b/packages/templating/plugin/html_scanner.js
index b45b6d3dd9..f5d8da082b 100644
--- a/packages/templating/plugin/html_scanner.js
+++ b/packages/templating/plugin/html_scanner.js
@@ -174,7 +174,7 @@ html_scanner = {
         if (hasAttribs) {
           for(var attr in attribs) {
             if (this.bodyAttributes.indexOf(attr) !== -1) {
-              console.log('WARNING: tag ' + attr + ' already defined on body.');
+              throwParseError('Tag ' + attr + ' already defined on body.');
             }
             this.bodyAttributes.push(attr);
           }