diff --git a/code/AssimpCExport.cpp b/code/AssimpCExport.cpp
index 9483eb2d3..053e1b9f4 100644
--- a/code/AssimpCExport.cpp
+++ b/code/AssimpCExport.cpp
@@ -73,6 +73,7 @@ ASSIMP_API void aiCopyScene(const aiScene* pIn, aiScene** pOut)
 	}
 
 	SceneCombiner::CopyScene(pOut,pIn,true);
+	ScenePriv(*pOut)->mIsCopy = true;
 }
 
 
diff --git a/code/ScenePrivate.h b/code/ScenePrivate.h
index dc11bb4fa..8e9fde7ac 100644
--- a/code/ScenePrivate.h
+++ b/code/ScenePrivate.h
@@ -53,6 +53,7 @@ struct ScenePrivateData {
 	ScenePrivateData()
 		: mOrigImporter()
 		, mPPStepsApplied()
+		, mIsCopy()
 	{}
 
 	// Importer that originally loaded the scene though the C-API
@@ -61,6 +62,13 @@ struct ScenePrivateData {
 
 	// List of postprocessing steps already applied to the scene.
 	unsigned int mPPStepsApplied;
+
+	// true if the scene is a copy made with aiCopyScene()
+	// or the corresponding C++ API. This means that user code
+	// may have made modifications to it, so mPPStepsApplied
+	// and mOrigImporter are no longer safe to rely on and only
+	// serve informative purposes.
+	bool mIsCopy;
 };
 
 // Access private data stored in the scene