Index: lib/redmine/search.rb
===================================================================
--- lib/redmine/search.rb	(revision 17633)
+++ lib/redmine/search.rb	(working copy)
@@ -59,8 +59,9 @@
         # extract tokens from the question
         # eg. hello "bye bye" => ["hello", "bye bye"]
         @tokens = @question.scan(%r{((\s|^)"[^"]+"(\s|$)|\S+)}).collect {|m| m.first.gsub(%r{(^\s*"\s*|\s*"\s*$)}, '')}
-        # tokens must be at least 2 characters long
-        @tokens = @tokens.uniq.select {|w| w.length > 1 }
+        # tokens must be at least 2 characters long for ASCII characters
+        # but single character tokens are allowed for multibyte characters
+        @tokens = @tokens.uniq.select {|w| w.bytesize > 1 }
         # no more than 5 tokens to search for
         @tokens.slice! 5..-1
       end
Index: test/unit/search_test.rb
===================================================================
--- test/unit/search_test.rb	(revision 17633)
+++ test/unit/search_test.rb	(working copy)
@@ -194,6 +194,11 @@
     assert_equal ['Special', 'chars', 'in a phrase Öö'], f.tokens
   end
 
+  def test_fetcher_should_ignore_too_short_tokens
+    f = Redmine::Search::Fetcher.new('x yz 雲 天空', User.anonymous, %w(issues), Project.all)
+    assert_equal ['yz', '雲', '天空'], f.tokens
+  end
+
   private
 
   def remove_permission(role, permission)