diff --git a/ChangeLog b/ChangeLog
index 1d9d6d6770..16e7119723 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri Apr 15 23:41:18 2011  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
+
+	* ruby.c (proc_options): reduce warning:
+	  "ALLOW_DEFAULT_SOURCE_ENCODING" is not defined.
+
 Fri Apr 15 15:10:29 2011  Akinori MUSHA  <knu@iDaemons.org>
 
 	* lib/uri/generic.rb (#route_from_path): Fix a bug where
diff --git a/ruby.c b/ruby.c
index 88305f03ef..3cfa2854c8 100644
--- a/ruby.c
+++ b/ruby.c
@@ -1017,7 +1017,7 @@ proc_options(long argc, char **argv, struct cmdline_options *opt, int envopt)
 		    if (!*(s = ++p)) break;
 		    set_encoding_part(internal);
 		    if (!*(s = ++p)) break;
-#if ALLOW_DEFAULT_SOURCE_ENCODING
+#if defined ALLOW_DEFAULT_SOURCE_ENCODING && ALLOW_DEFAULT_SOURCE_ENCODING
 		    set_encoding_part(source);
 		    if (!*(s = ++p)) break;
 #endif
@@ -1032,7 +1032,7 @@ proc_options(long argc, char **argv, struct cmdline_options *opt, int envopt)
 	    else if (is_option_with_arg("external-encoding", Qfalse, Qtrue)) {
 		set_external_encoding_once(opt, s, 0);
 	    }
-#if ALLOW_DEFAULT_SOURCE_ENCODING
+#if defined ALLOW_DEFAULT_SOURCE_ENCODING && ALLOW_DEFAULT_SOURCE_ENCODING
 	    else if (is_option_with_arg("source-encoding", Qfalse, Qtrue)) {
 		set_source_encoding_once(opt, s, 0);
 	    }