--- a/gfx/webrender_bindings/src/bindings.rs
+++ b/gfx/webrender_bindings/src/bindings.rs
@@ -815,17 +815,18 @@ pub extern "C" fn wr_api_set_root_pipeli
 
 #[no_mangle]
 pub extern "C" fn wr_api_set_window_parameters(dh: &mut DocumentHandle,
                                                width: i32,
                                                height: i32) {
     let size = DeviceUintSize::new(width as u32, height as u32);
     dh.api.set_window_parameters(dh.document_id,
                                  size,
-                                 DeviceUintRect::new(DeviceUintPoint::new(0, 0), size));
+                                 DeviceUintRect::new(DeviceUintPoint::new(0, 0), size),
+                                 1.0);
 }
 
 #[no_mangle]
 pub unsafe extern "C" fn wr_api_set_display_list(
     dh: &mut DocumentHandle,
     color: ColorF,
     epoch: WrEpoch,
     viewport_width: f32,