diff --git a/demo/startup.js b/demo/startup.js
index c56a8dc6..d0f3db5f 100644
--- a/demo/startup.js
+++ b/demo/startup.js
@@ -171,7 +171,7 @@ exports.launch = function(env) {
     });
 
     bindDropdown("fontsize", function(value) {
-        document.getElementById("editor").style["font-size"] = value;
+        document.getElementById("editor").style.fontSize = value;
     });
 
     bindDropdown("soft_wrap", function(value) {