diff --git a/ChangeLog b/ChangeLog
index 9acc532244..e20c3f4850 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -29,6 +29,11 @@ Tue Oct 14 20:32:09 2008  Tanaka Akira  <akr@fsij.org>
 	  from transcode_tblgen_windows.
 	  (transcode_tblgen_iso8859): use transcode_tblgen_singlebyte.
 
+Tue Oct 14 19:32:14 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* ruby.c (process_options): -U should be allowed in RUBYOPT
+	  environment variable.  [ruby-dev:36720]
+
 Tue Oct 14 14:11:17 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ruby.c (proc_options): -U can be followed by other options.
diff --git a/ruby.c b/ruby.c
index 5420b94aa2..edce4777bc 100644
--- a/ruby.c
+++ b/ruby.c
@@ -1043,7 +1043,7 @@ process_options(VALUE arg)
 		}
 		if (!*s)
 		    break;
-		if (!strchr("EIdvwWrK", *s))
+		if (!strchr("EIdvwWrKU", *s))
 		    rb_raise(rb_eRuntimeError,
 			     "invalid switch in RUBYOPT: -%c", *s);
 		s = moreswitches(s, opt);