diff --git a/main.js b/main.js
index 4536c1d63..ad9e8a5de 100644
--- a/main.js
+++ b/main.js
@@ -8,7 +8,7 @@ window.startup = function() {
     var demoOutput = document.getElementById("demo-output");
 
     function doDemo() {
-        katex.render("\\displaystyle " + demoInput.value, demoOutput);
+        katex.render("\\displaystyle{" + demoInput.value + "}", demoOutput);
     }
 
     demoInput.addEventListener("input", function() {