diff --git a/configure.in b/configure.in
index d2a8228..b80f596 100644
--- a/configure.in
+++ b/configure.in
@@ -1064,6 +1064,10 @@ AC_CHECK_TYPES([struct timespec], [], [], [@%:@ifdef HAVE_TIME_H
 @%:@include <time.h>
 @%:@endif])
 
+AC_CHECK_TYPES([struct timezone], [], [], [@%:@ifdef HAVE_TIME_H
+@%:@include <time.h>
+@%:@endif])
+
 AC_CHECK_TYPE(fd_mask, [AC_DEFINE(HAVE_RB_FD_INIT, 1)])
 
 dnl RUBY_DEFINT TYPENAME, SIZE, [SIGNED-OR-UNSIGNED], [INCLUDES = DEFAULT-INCLUDES]
diff --git a/include/ruby/win32.h b/include/ruby/win32.h
index 5f0501a..e003484 100644
--- a/include/ruby/win32.h
+++ b/include/ruby/win32.h
@@ -197,11 +197,14 @@ extern int rb_w32_fstat(int, struct stat *);
 #define strncasecmp		_strnicmp
 #define fsync			_commit
 
-#ifdef __MINGW32__
+#if !defined(HAVE_STRUCT_TIMEZONE)
 struct timezone {
   int tz_minuteswest;
   int tz_dsttime;
 };
+#endif
+
+#if defined(__MINGW32__)
 #undef isascii
 #define isascii __isascii
 #endif