diff --git a/dlls/mfplat/main.c b/dlls/mfplat/main.c
index a8963ca0d82..0bf7cbf4c9a 100644
--- a/dlls/mfplat/main.c
+++ b/dlls/mfplat/main.c
@@ -4165,3 +4165,13 @@ void WINAPI MFHeapFree(void *p)
     TRACE("%p\n", p);
     HeapFree(GetProcessHeap(), 0, p);
 }
+
+/***********************************************************************
+ *      MFCreateMFByteStreamOnStreamEx (mfplat.@)
+ */
+HRESULT WINAPI MFCreateMFByteStreamOnStreamEx(IUnknown *stream, IMFByteStream **bytestream)
+{
+    FIXME("(%p, %p): stub\n", stream, bytestream);
+
+    return E_NOTIMPL;
+}
diff --git a/dlls/mfplat/mfplat.spec b/dlls/mfplat/mfplat.spec
index c43746ec7b4..c6234b006e5 100644
--- a/dlls/mfplat/mfplat.spec
+++ b/dlls/mfplat/mfplat.spec
@@ -46,6 +46,7 @@
 @ stdcall MFCreateFile(long long long wstr ptr)
 @ stub MFCreateLegacyMediaBufferOnMFMediaBuffer
 @ stdcall MFCreateMFByteStreamOnStream(ptr ptr)
+@ stdcall MFCreateMFByteStreamOnStreamEx(ptr ptr)
 @ stub MFCreateMFVideoFormatFromMFMediaType
 @ stub MFCreateMediaBufferWrapper
 @ stdcall MFCreateMediaEvent(long ptr long ptr ptr)
diff --git a/include/mfidl.idl b/include/mfidl.idl
index c8f011bb777..01e86efc518 100644
--- a/include/mfidl.idl
+++ b/include/mfidl.idl
@@ -318,6 +318,7 @@ interface IMFSequencerSource : IUnknown
 
 cpp_quote("HRESULT WINAPI MFCreateMediaSession(IMFAttributes *config, IMFMediaSession **session);")
 cpp_quote("HRESULT WINAPI MFCreateMFByteStreamOnStream(IStream *stream, IMFByteStream **bytestream);" )
+cpp_quote("HRESULT WINAPI MFCreateMFByteStreamOnStreamEx(IUnknown *stream, IMFByteStream **bytestream);")
 cpp_quote("HRESULT WINAPI MFCreateSequencerSource(IUnknown *reserved, IMFSequencerSource **seq_source);" )
 cpp_quote("HRESULT WINAPI MFCreateSourceResolver(IMFSourceResolver **resolver);")
 cpp_quote("HRESULT WINAPI MFCreateStreamDescriptor(DWORD identifier, DWORD cMediaTypes,")