diff --git a/reactos/include/psdk/oleauto.h b/reactos/include/psdk/oleauto.h
index 4492d040744..98e8dbf57ad 100644
--- a/reactos/include/psdk/oleauto.h
+++ b/reactos/include/psdk/oleauto.h
@@ -316,7 +316,7 @@ HRESULT WINAPI VarR8FromUI4(ULONG,double*);
 HRESULT WINAPI VarR8FromUI8(ULONG64,double*);
 HRESULT WINAPI VarR8FromStr(OLECHAR*,LCID,ULONG,double*);
 HRESULT WINAPI VarR8FromCy(CY,double*);
-HRESULT WINAPI VarR8FromDec(DECIMAL*,double*);
+HRESULT WINAPI VarR8FromDec(const DECIMAL*,double*);
 HRESULT WINAPI VarR8FromDisp(IDispatch*,LCID,double*);
 
 HRESULT WINAPI VarDateFromUI1(BYTE,DATE*);