diff --git a/src/os_unix.c b/src/os_unix.c
index 425498c..001f085 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -49,7 +49,7 @@
 #endif
 
 #ifdef __CYGWIN__
-# ifndef WIN32
+# ifndef MSWIN
 #  include <cygwin/version.h>
 #  include <sys/cygwin.h>	/* for cygwin_conv_to_posix_path() and/or
 				 * for cygwin_conv_path() */