diff --git a/include/wine/obj_storage.h b/include/wine/obj_storage.h
index dd37ca71aac..6213cc6064f 100644
--- a/include/wine/obj_storage.h
+++ b/include/wine/obj_storage.h
@@ -693,6 +693,7 @@ HRESULT WINAPI StgOpenStorage16(const OLECHAR16* pwcsName,IStorage16* pstgPriori
 HRESULT WINAPI StgOpenStorage(const OLECHAR* pwcsName,IStorage* pstgPriority,DWORD grfMode,SNB snbExclude,DWORD reserved,IStorage**ppstgOpen);
 
 HRESULT WINAPI WriteClassStg(IStorage* pStg, REFCLSID rclsid);
+HRESULT WINAPI ReadClassStg(IStorage *pstg,CLSID *pclsid);
 
 HRESULT WINAPI StgCreateDocfileOnILockBytes(ILockBytes *plkbyt,DWORD grfMode, DWORD reserved, IStorage** ppstgOpen);
 HRESULT WINAPI StgOpenStorageOnILockBytes(ILockBytes *plkbyt, IStorage *pstgPriority, DWORD grfMode, SNB snbExclude, DWORD reserved, IStorage **ppstgOpen);