diff --git a/template/viewer.html b/template/viewer.html
index 9e6d539..7551673 100644
--- a/template/viewer.html
+++ b/template/viewer.html
@@ -34,7 +34,7 @@ <h2>{{name}}</h2>
 			{{#rules}}
 			  <div class="rule">
 					<h3 id={{name}}>{{name}}</h3>
-					<div onclick=svgBlockClick>
+					<div onclick="svgBlockClick(event)">
 						{{{diagram}}}
 					</div>
 					<div>