Index: lib/sdk/crt/stdio/file.c
===================================================================
--- lib/sdk/crt/stdio/file.c	(revision 64892)
+++ lib/sdk/crt/stdio/file.c	(working copy)
@@ -3690,7 +3690,9 @@
 int CDECL setvbuf(FILE* file, char *buf, int mode, size_t size)
 {
     if(!MSVCRT_CHECK_PMT(file != NULL)) return -1;
+#ifndef __REACTOS__ /* CORE-8670 */
     if(!MSVCRT_CHECK_PMT(mode==_IONBF || mode==_IOFBF || mode==_IOLBF)) return -1;
+#endif
     if(!MSVCRT_CHECK_PMT(mode==_IONBF || (size>=2 && size<=INT_MAX))) return -1;
 
     _lock_file(file);