diff --git a/ChangeLog b/ChangeLog
index a860bf88df..2dc3608a9f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Wed Oct  8 04:33:04 2014  Rei Odaira  <Rei.Odaira@gmail.com>
+
+	* test/ruby/test_rubyoptions.rb (TestRubyOptions#test_encoding):
+	  On AIX, locale_charmap is ISO-8859-1 with LANG=C.  This means
+	  the source encoding of stdin is ISO-8859-1, so "invalid
+	  multibyte char" error does not occur.
+
 Wed Oct  8 04:30:29 2014  Marc-Andre Lafortune  <ruby-core@marc-andre.ca>
 
 	* lib/matrix.rb: Add Matrix#laplace_expansion.
diff --git a/test/ruby/test_rubyoptions.rb b/test/ruby/test_rubyoptions.rb
index 22bbcf02ed..2dc7a0b315 100644
--- a/test/ruby/test_rubyoptions.rb
+++ b/test/ruby/test_rubyoptions.rb
@@ -209,10 +209,12 @@ class TestRubyOptions < Test::Unit::TestCase
     assert_in_out_err(%w(--encoding test_ruby_test_rubyoptions_foobarbazqux), "", [],
                       /unknown encoding name - test_ruby_test_rubyoptions_foobarbazqux \(RuntimeError\)/)
 
-    if /mswin|mingw/ =~ RUBY_PLATFORM &&
+    if /mswin|mingw|aix/ =~ RUBY_PLATFORM &&
       (str = "\u3042".force_encoding(Encoding.find("locale"))).valid_encoding?
       # This result depends on locale because LANG=C doesn't affect locale
       # on Windows.
+      # On AIX, the source encoding of stdin with LANG=C is ISO-8859-1,
+      # which allows \u3042.
       out, err = [str], []
     else
       out, err = [], /invalid multibyte char/