diff --git a/ChangeLog b/ChangeLog
index d6d1946d57..c5ad5eb5a7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sat Dec  6 21:45:10 2003  WATANABE Hirofumi  <eban@ruby-lang.org>
+
+	* io.c (flush_before_seek): flush before seek on any platform.
+
+	* configure.in: ditto.
+
 Sat Dec  6 17:23:00 2003  NAKAMURA, Hiroshi  <nahi@ruby-lang.org>
 
 	* lib/soap/soap.rb(SOAP::Env.getenv): allow upcase environment variable
diff --git a/configure.in b/configure.in
index 23149915e4..74f9b4b348 100644
--- a/configure.in
+++ b/configure.in
@@ -636,10 +636,10 @@ RUBY_CHECK_IO_NEED(seek between R/W, rb_cv_need_io_seek_between_rw, yes)
 if test "$rb_cv_need_io_seek_between_rw" = yes; then
   AC_DEFINE(NEED_IO_SEEK_BETWEEN_RW, 1)
 fi
-RUBY_CHECK_IO_NEED(flush before seek, rb_cv_need_io_flush_before_seek, no)
-if test "$rb_cv_need_io_flush_before_seek" = yes; then
-  AC_DEFINE(NEED_IO_FLUSH_BEFORE_SEEK, 1)
-fi
+dnl RUBY_CHECK_IO_NEED(flush before seek, rb_cv_need_io_flush_before_seek, no)
+dnl if test "$rb_cv_need_io_flush_before_seek" = yes; then
+dnl   AC_DEFINE(NEED_IO_FLUSH_BEFORE_SEEK, 1)
+dnl fi
 
 AC_CACHE_CHECK([whether st_ino is huge], rb_cv_huge_st_ino,
 [AC_COMPILE_IFELSE([AC_LANG_BOOL_COMPILE_TRY([
diff --git a/io.c b/io.c
index 639e207693..06d9283102 100644
--- a/io.c
+++ b/io.c
@@ -194,7 +194,6 @@ rb_io_check_closed(fptr)
 
 static void io_fflush _((FILE *, OpenFile *));
 
-#if NEED_IO_FLUSH_BEFORE_SEEK
 static OpenFile *
 flush_before_seek(fptr)
     OpenFile *fptr;
@@ -204,9 +203,6 @@ flush_before_seek(fptr)
     }
     return fptr;
 }
-#else
-#define flush_before_seek(fptr) fptr
-#endif
 
 #define io_seek(fptr, ofs, whence) fseeko(flush_before_seek(fptr)->f, ofs, whence)
 #define io_tell(fptr) ftello(flush_before_seek(fptr)->f)