diff --git a/RenderSystems/NULL/include/OgreNULLTextureGpu.h b/RenderSystems/NULL/include/OgreNULLTextureGpu.h
index 35a7f333d23..f80ac353c6e 100644
--- a/RenderSystems/NULL/include/OgreNULLTextureGpu.h
+++ b/RenderSystems/NULL/include/OgreNULLTextureGpu.h
@@ -86,6 +86,22 @@ namespace Ogre
         PixelFormatGpu getDesiredDepthBufferFormat() const override;
     };
 
+    /// A RenderWindow-specific texture. Its only job over the base class is to
+    /// answer the "Window" custom attribute, which RenderSystem::getDepthBufferFor
+    /// relies on for every render-window-specific colour target.
+    class _OgreNULLExport NULLTextureGpuWindow final : public NULLTextureGpuRenderTarget
+    {
+        Window *mWindow;
+
+    public:
+        NULLTextureGpuWindow( GpuPageOutStrategy::GpuPageOutStrategy pageOutStrategy,
+                              VaoManager *vaoManager, IdString name, uint32 textureFlags,
+                              TextureTypes::TextureTypes initialType, TextureGpuManager *textureManager,
+                              Window *window );
+
+        void getCustomAttribute( IdString name, void *pData ) override;
+    };
+
     /** @} */
     /** @} */
 }  // namespace Ogre
diff --git a/RenderSystems/NULL/include/OgreNULLTextureGpuManager.h b/RenderSystems/NULL/include/OgreNULLTextureGpuManager.h
index b41e4c43ec1..f30290bd54b 100644
--- a/RenderSystems/NULL/include/OgreNULLTextureGpuManager.h
+++ b/RenderSystems/NULL/include/OgreNULLTextureGpuManager.h
@@ -64,7 +64,7 @@ namespace Ogre
         NULLTextureGpuManager( VaoManager *vaoManager, RenderSystem *renderSystem );
         ~NULLTextureGpuManager() override;
 
-        TextureGpu *createTextureGpuWindow();
+        TextureGpu *createTextureGpuWindow( Window *window );
     };
 
     /** @} */
diff --git a/RenderSystems/NULL/src/OgreNULLTextureGpu.cpp b/RenderSystems/NULL/src/OgreNULLTextureGpu.cpp
index c41b0f9a49f..6bbc6dbfdb6 100644
--- a/RenderSystems/NULL/src/OgreNULLTextureGpu.cpp
+++ b/RenderSystems/NULL/src/OgreNULLTextureGpu.cpp
@@ -102,4 +102,23 @@ namespace Ogre
     {
         return mDesiredDepthBufferFormat;
     }
+    //-----------------------------------------------------------------------------------
+    //-----------------------------------------------------------------------------------
+    //-----------------------------------------------------------------------------------
+    NULLTextureGpuWindow::NULLTextureGpuWindow( GpuPageOutStrategy::GpuPageOutStrategy pageOutStrategy,
+                                                VaoManager *vaoManager, IdString name,
+                                                uint32 textureFlags,
+                                                TextureTypes::TextureTypes initialType,
+                                                TextureGpuManager *textureManager, Window *window ) :
+        NULLTextureGpuRenderTarget( pageOutStrategy, vaoManager, name, textureFlags, initialType,
+                                    textureManager ),
+        mWindow( window )
+    {
+    }
+    //-----------------------------------------------------------------------------------
+    void NULLTextureGpuWindow::getCustomAttribute( IdString name, void *pData )
+    {
+        if( name == "Window" )
+            *static_cast<Window **>( pData ) = mWindow;
+    }
 }  // namespace Ogre
diff --git a/RenderSystems/NULL/src/OgreNULLTextureGpuManager.cpp b/RenderSystems/NULL/src/OgreNULLTextureGpuManager.cpp
index 9a222c23a79..c0543dddd99 100644
--- a/RenderSystems/NULL/src/OgreNULLTextureGpuManager.cpp
+++ b/RenderSystems/NULL/src/OgreNULLTextureGpuManager.cpp
@@ -45,13 +45,13 @@ namespace Ogre
     //-----------------------------------------------------------------------------------
     NULLTextureGpuManager::~NULLTextureGpuManager() { destroyAll(); }
     //-----------------------------------------------------------------------------------
-    TextureGpu *NULLTextureGpuManager::createTextureGpuWindow()
+    TextureGpu *NULLTextureGpuManager::createTextureGpuWindow( Window *window )
     {
-        return OGRE_NEW NULLTextureGpuRenderTarget(
-            GpuPageOutStrategy::Discard, mVaoManager, "RenderWindow",
-            TextureFlags::NotTexture | TextureFlags::RenderToTexture |
-                TextureFlags::RenderWindowSpecific | TextureFlags::DiscardableContent,
-            TextureTypes::Type2D, this );
+        return OGRE_NEW NULLTextureGpuWindow( GpuPageOutStrategy::Discard, mVaoManager, "RenderWindow",
+                                              TextureFlags::NotTexture | TextureFlags::RenderToTexture |
+                                                  TextureFlags::RenderWindowSpecific |
+                                                  TextureFlags::DiscardableContent,
+                                              TextureTypes::Type2D, this, window );
     }
     //-----------------------------------------------------------------------------------
     TextureGpu *NULLTextureGpuManager::createTextureImpl(
diff --git a/RenderSystems/NULL/src/OgreNULLWindow.cpp b/RenderSystems/NULL/src/OgreNULLWindow.cpp
index ae05f991f88..65f5e5f6f39 100644
--- a/RenderSystems/NULL/src/OgreNULLWindow.cpp
+++ b/RenderSystems/NULL/src/OgreNULLWindow.cpp
@@ -95,8 +95,8 @@ namespace Ogre
         NULLTextureGpuManager *textureManager =
             static_cast<NULLTextureGpuManager *>( textureGpuManager );
 
-        mTexture = textureManager->createTextureGpuWindow();
-        mDepthBuffer = textureManager->createTextureGpuWindow();
+        mTexture = textureManager->createTextureGpuWindow( this );
+        mDepthBuffer = textureManager->createTextureGpuWindow( this );
         mStencilBuffer = mDepthBuffer;
 
         setFinalResolution( mRequestedWidth, mRequestedHeight );