diff --git a/regint.h b/regint.h
index 344ece4ef1..624deea864 100644
--- a/regint.h
+++ b/regint.h
@@ -202,7 +202,7 @@
 #define xmemcpy     memcpy
 #define xmemmove    memmove
 
-#if defined(_WIN32) && !defined(__GNUC__)
+#if defined(RUBY_MSVCRT_VERSION) && RUBY_MSVCRT_VERSION >= 90 && !defined(__GNUC__)
 # define xalloca     _alloca
 # define xvsnprintf(buf,size,fmt,args)  _vsnprintf_s(buf,size,_TRUNCATE,fmt,args)
 # define xsnprintf   sprintf_s