diff --git a/gfx/webrender_bindings/RendererOGL.cpp b/gfx/webrender_bindings/RendererOGL.cpp
index ec9d2eb9102c..250ad7d274d4 100644
--- a/gfx/webrender_bindings/RendererOGL.cpp
+++ b/gfx/webrender_bindings/RendererOGL.cpp
@@ -16,7 +16,7 @@
 namespace mozilla {
 namespace wr {
 
-WrExternalImage LockExternalImage(void* aObj, WrExternalImageId aId)
+WrExternalImage LockExternalImage(void* aObj, WrExternalImageId aId, uint8_t aChannelIndex)
 {
   RendererOGL* renderer = reinterpret_cast<RendererOGL*>(aObj);
   RenderTextureHost* texture = renderer->GetRenderTexture(aId);
@@ -42,7 +42,7 @@ WrExternalImage LockExternalImage(void* aObj, WrExternalImageId aId)
   }
 }
 
-void UnlockExternalImage(void* aObj, WrExternalImageId aId)
+void UnlockExternalImage(void* aObj, WrExternalImageId aId, uint8_t aChannelIndex)
 {
   RendererOGL* renderer = reinterpret_cast<RendererOGL*>(aObj);
   RenderTextureHost* texture = renderer->GetRenderTexture(aId);
diff --git a/gfx/webrender_bindings/RendererOGL.h b/gfx/webrender_bindings/RendererOGL.h
index e28e34405d57..b3da5a4ca8ce 100644
--- a/gfx/webrender_bindings/RendererOGL.h
+++ b/gfx/webrender_bindings/RendererOGL.h
@@ -40,8 +40,8 @@ class RenderTextureHost;
 /// on the render thread instead of the compositor thread.
 class RendererOGL
 {
-  friend WrExternalImage LockExternalImage(void* aObj, WrExternalImageId aId);
-  friend void UnlockExternalImage(void* aObj, WrExternalImageId aId);
+  friend WrExternalImage LockExternalImage(void* aObj, WrExternalImageId aId, uint8_t aChannelIndex);
+  friend void UnlockExternalImage(void* aObj, WrExternalImageId aId, uint8_t aChannelIndex);
 
 public:
   WrExternalImageHandler GetExternalImageHandler();
diff --git a/gfx/webrender_bindings/src/bindings.rs b/gfx/webrender_bindings/src/bindings.rs
index ec9acffbfd1f..4c6645b87cc3 100644
--- a/gfx/webrender_bindings/src/bindings.rs
+++ b/gfx/webrender_bindings/src/bindings.rs
@@ -555,8 +555,8 @@ struct WrExternalImage {
     size: usize,
 }
 
-type LockExternalImageCallback = fn(*mut c_void, WrExternalImageId) -> WrExternalImage;
-type UnlockExternalImageCallback = fn(*mut c_void, WrExternalImageId);
+type LockExternalImageCallback = fn(*mut c_void, WrExternalImageId, u8) -> WrExternalImage;
+type UnlockExternalImageCallback = fn(*mut c_void, WrExternalImageId, u8);
 
 #[repr(C)]
 pub struct WrExternalImageHandler {
@@ -568,9 +568,9 @@ pub struct WrExternalImageHandler {
 impl ExternalImageHandler for WrExternalImageHandler {
     fn lock(&mut self,
             id: ExternalImageId,
-            _channel_index: u8)
+            channel_index: u8)
             -> ExternalImage {
-        let image = (self.lock_func)(self.external_image_obj, id.into());
+        let image = (self.lock_func)(self.external_image_obj, id.into(), channel_index);
 
         match image.image_type {
             WrExternalImageType::NativeTexture => {
@@ -596,8 +596,8 @@ impl ExternalImageHandler for WrExternalImageHandler {
 
     fn unlock(&mut self,
               id: ExternalImageId,
-              _channel_index: u8) {
-        (self.unlock_func)(self.external_image_obj, id.into());
+              channel_index: u8) {
+        (self.unlock_func)(self.external_image_obj, id.into(), channel_index);
     }
 }
 
diff --git a/gfx/webrender_bindings/webrender_ffi_generated.h b/gfx/webrender_bindings/webrender_ffi_generated.h
index 82d7fc3324a3..b79fc0748672 100644
--- a/gfx/webrender_bindings/webrender_ffi_generated.h
+++ b/gfx/webrender_bindings/webrender_ffi_generated.h
@@ -485,9 +485,9 @@ struct WrExternalImage {
   }
 };
 
-typedef WrExternalImage (*LockExternalImageCallback)(void*, WrExternalImageId);
+typedef WrExternalImage (*LockExternalImageCallback)(void*, WrExternalImageId, uint8_t);
 
-typedef void (*UnlockExternalImageCallback)(void*, WrExternalImageId);
+typedef void (*UnlockExternalImageCallback)(void*, WrExternalImageId, uint8_t);
 
 struct WrExternalImageHandler {
   void* external_image_obj;