--- a/testing/marionette/driver.js
+++ b/testing/marionette/driver.js
@@ -2485,18 +2485,18 @@ GeckoDriver.prototype.getWindowSize = fu
  * An error will be returned if the requested window size would result
  * in the window being in the maximized state.
  */
 GeckoDriver.prototype.setWindowSize = function(cmd, resp) {
   if (this.appName != "Firefox") {
     throw new UnsupportedOperationError();
   }
 
-  let width = parseInt(cmd.parameters.width);
-  let height = parseInt(cmd.parameters.height);
+  let width = cmd.parameters.width;
+  let height = cmd.parameters.height;
 
   let win = this.getCurrentWindow();
   if (width >= win.screen.availWidth || height >= win.screen.availHeight) {
     throw new UnsupportedOperationError("Requested size exceeds screen size")
   }
 
   win.resizeTo(width, height);
 };