diff --git a/ChangeLog b/ChangeLog
index 9312462438..833b2a7713 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue May  3 22:19:55 2016  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* configure.in (warnflags): use -std=gnu99 instead of
+	  -std=iso9899:1999. [Feature #12336]
+
 Tue May  3 22:10:09 2016  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* string.c (count_utf8_lead_bytes_with_word): Use __builtin_popcount
diff --git a/configure.in b/configure.in
index ad8cc988c4..43af2bdced 100644
--- a/configure.in
+++ b/configure.in
@@ -916,7 +916,7 @@ if test "$GCC" = yes; then
     ],
     [
       # ANSI (no XCFLAGS because this is C only)
-	for ansi_options in -std=iso9899:1999 "-ansi -std=iso9899:199409"; do
+	for ansi_options in -std=gnu99; do
 	    RUBY_TRY_CFLAGS(${ansi_options}, [
 		RUBY_APPEND_OPTIONS(warnflags, ${ansi_options})
 		RUBY_APPEND_OPTIONS(strict_warnflags, ${ansi_options})