diff --git a/src/include/port.h b/src/include/port.h
index cb13dd80c7..455f72338c 100644
--- a/src/include/port.h
+++ b/src/include/port.h
@@ -214,12 +214,12 @@ extern int	pgkill(int pid, int sig);
 extern int	pclose_check(FILE *stream);
 
 /* Global variable holding time zone information. */
-#ifndef __CYGWIN__
-#define TIMEZONE_GLOBAL timezone
-#define TZNAME_GLOBAL tzname
-#else
+#if defined(WIN32) || defined(__CYGWIN__)
 #define TIMEZONE_GLOBAL _timezone
 #define TZNAME_GLOBAL _tzname
+#else
+#define TIMEZONE_GLOBAL timezone
+#define TZNAME_GLOBAL tzname
 #endif
 
 #if defined(WIN32) || defined(__CYGWIN__)