diff --git a/ChangeLog b/ChangeLog
index 916ea54569..268e1cbdac 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Jun 30 21:18:35 2011  Yutaka Kanemoto  <kanemoto@ruby-lang.org>
+
+	* configure.in: Add warnflags for XL/C on AIX during configure
+	  to avoid [Bug #3971]. See [ruby-core:32859]
+
 Thu Jun 30 21:16:04 2011  Tadayoshi Funaba  <tadf@dotrb.org>
 
 	* ext/date/date_core.c (m_ajd): refers a constant.
diff --git a/configure.in b/configure.in
index 7f74fd16b3..2185174851 100644
--- a/configure.in
+++ b/configure.in
@@ -474,6 +474,9 @@ if test "$GCC:${warnflags+set}:no" = yes::no; then
     rb_cv_warnflags="$warnflags"
     warnflags=
 fi
+if test "$GCC" = ""; then
+    AS_CASE(["$target_os"],[aix*],[warnflags="-qinfo=por"])
+fi
 if test "$GCC" = yes; then
     RUBY_TRY_CFLAGS(-fvisibility=hidden, [RUBY_APPEND_OPTION(XCFLAGS, -fvisibility=hidden)])
     AC_SUBST(WERRORFLAG, "-Werror")