diff --git a/ChangeLog b/ChangeLog
index 50af290abe..f868531fc7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Thu Nov 25 18:06:37 2004  Tanaka Akira  <akr@m17n.org>
+
+	* configure.in: AC_CHECK_SIZEOF(rlim_t) to include stdio.h to fix
+	  problem with autoconf 2.52 or earlier.
+	  revert AC_PREREQ to 2.50.
+
 Thu Nov 25 07:59:41 2004  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* configure.in: AC_PREREQ(2.53) [ruby-core:03800]
diff --git a/configure.in b/configure.in
index 57ab6bf4d9..ac76c4bcf3 100644
--- a/configure.in
+++ b/configure.in
@@ -1,7 +1,7 @@
 dnl Process this file with autoconf to produce a configure script.
 AC_INIT()
 
-AC_PREREQ(2.53)
+AC_PREREQ(2.50)
 
 AC_DEFUN(RUBY_MINGW32,
 [case "$host_os" in
@@ -410,6 +410,7 @@ AC_CHECK_SIZEOF(rlim_t, 0, [
   #ifdef HAVE_UNISTD_H
   # include <unistd.h>
   #endif
+  #include <stdio.h>
 ])
 
 dnl Checks for typedefs, structures, and compiler characteristics.