--- a/testing/marionette/interaction.js
+++ b/testing/marionette/interaction.js
@@ -277,17 +277,17 @@ function* seleniumClickElement(el, a11y)
  *     If <var>el</var> is a XUL element or not an <tt>&lt;option&gt;</tt>
  *     element.
  * @throws {Error}
  *     If unable to find <var>el</var>'s parent <tt>&lt;select&gt;</tt>
  *     element.
  */
 interaction.selectOption = function(el) {
   if (element.isXULElement(el)) {
-    throw new Error("XUL dropdowns not supported");
+    throw new TypeError("XUL dropdowns not supported");
   }
   if (el.localName != "option") {
     throw new TypeError(pprint`Expected <option> element, got ${el}`);
   }
 
   let containerEl = element.getContainer(el);
 
   event.mouseover(containerEl);