--- a/gfx/webrender_bindings/src/bindings.rs
+++ b/gfx/webrender_bindings/src/bindings.rs
@@ -544,17 +544,18 @@ type UnlockExternalImageCallback = fn(*m
 pub struct WrExternalImageHandler {
     external_image_obj: *mut c_void,
     lock_func: LockExternalImageCallback,
     unlock_func: UnlockExternalImageCallback,
 }
 
 impl ExternalImageHandler for WrExternalImageHandler {
     fn lock(&mut self,
-            id: ExternalImageId)
+            id: ExternalImageId,
+            _channel_index: u8)
             -> ExternalImage {
         let image = (self.lock_func)(self.external_image_obj, id.into());
 
         match image.image_type {
             WrExternalImageType::NativeTexture => {
                 ExternalImage {
                     u0: image.u0,
                     v0: image.v0,
@@ -571,17 +572,18 @@ impl ExternalImageHandler for WrExternal
                     v1: image.v1,
                     source: ExternalImageSource::RawData(unsafe { slice::from_raw_parts(image.buff, image.size) }),
                 }
             },
         }
     }
 
     fn unlock(&mut self,
-              id: ExternalImageId) {
+              id: ExternalImageId,
+              _channel_index: u8) {
         (self.unlock_func)(self.external_image_obj, id.into());
     }
 }
 
 /// cbindgen:field-names=[mHandle]
 /// cbindgen:struct-gen-op-lt=true
 /// cbindgen:struct-gen-op-lte=true
 #[repr(C)]
@@ -928,31 +930,33 @@ pub extern "C" fn wr_api_add_external_im
                                                    image_key: WrImageKey,
                                                    descriptor: &WrImageDescriptor,
                                                    external_image_id: WrExternalImageId) {
     assert!(unsafe { is_in_compositor_thread() });
     api.add_image(image_key,
                   descriptor.into(),
                   ImageData::External(ExternalImageData {
                                           id: external_image_id.into(),
+                                          channel_index: 0,
                                           image_type: ExternalImageType::Texture2DHandle,
                                       }),
                   None);
 }
 
 #[no_mangle]
 pub extern "C" fn wr_api_add_external_image_buffer(api: &mut WrAPI,
                                                    image_key: WrImageKey,
                                                    descriptor: &WrImageDescriptor,
                                                    external_image_id: WrExternalImageId) {
     assert!(unsafe { is_in_compositor_thread() });
     api.add_image(image_key,
                   descriptor.into(),
                   ImageData::External(ExternalImageData {
                                           id: external_image_id.into(),
+                                          channel_index: 0,
                                           image_type: ExternalImageType::ExternalBuffer,
                                       }),
                   None);
 }
 
 #[no_mangle]
 pub extern "C" fn wr_api_update_image(api: &mut WrAPI,
                                       key: WrImageKey,