diff --git a/include/winbase.h b/include/winbase.h
index ec54005..d518a00 100644
--- a/include/winbase.h
+++ b/include/winbase.h
@@ -1496,6 +1496,7 @@
 VOID        WINAPI Sleep(DWORD);
 DWORD       WINAPI SleepEx(DWORD,BOOL);
 DWORD       WINAPI SuspendThread(HANDLE);
+BOOL        WINAPI SwitchToThread(void);
 BOOL        WINAPI SystemTimeToFileTime(const SYSTEMTIME*,LPFILETIME);
 DWORD       WINAPI TlsAlloc(void);
 BOOL        WINAPI TlsFree(DWORD);