diff --git a/core/flyout_button.js b/core/flyout_button.js
index 93b1505a8..ca3d49ab6 100644
--- a/core/flyout_button.js
+++ b/core/flyout_button.js
@@ -95,7 +95,7 @@ Blockly.FlyoutButton = function(workspace, targetWorkspace, xml, isLabel) {
    * @type {?string}
    * @private
    */
-  this.cssClass_ = xml.getAttribute('class') || null;
+  this.cssClass_ = xml.getAttribute('web-style') || null;
 };
 
 /**
diff --git a/tests/playground.html b/tests/playground.html
index 0167e89a1..66a3e2514 100644
--- a/tests/playground.html
+++ b/tests/playground.html
@@ -591,7 +591,7 @@ h1 {
           </shadow>
         </value>
       </block>
-      <label text="Input/Output:" class="ioLabel"></label>
+      <label text="Input/Output:" web-style="ioLabel"></label>
       <block type="text_print">
         <value name="TEXT">
           <shadow type="text">