diff --git a/app/helpers/repositories_helper.rb b/app/helpers/repositories_helper.rb
index 27a3f78b..c6727ae2 100644
--- a/app/helpers/repositories_helper.rb
+++ b/app/helpers/repositories_helper.rb
@@ -117,16 +117,15 @@ module RepositoriesHelper
   end
   
   def to_utf8(str)
-    return str if str.blank?
+    return str if str.nil? 
+    if str.respond_to?(:force_encoding)
+      str.force_encoding('ASCII-8BIT')
+    end
+    return str if str.empty?
+    return str if /\A[\r\n\t\x20-\x7e]*\Z/n.match(str) # for us-ascii
     if str.respond_to?(:force_encoding)
       str.force_encoding('UTF-8')
-    else
-      # TODO:
-      # Japanese Shift_JIS(CP932) is not compatible with ASCII.      
-      # UTF-7 and Japanese ISO-2022-JP are 7bits clean.
-      return str if /\A[\r\n\t\x20-\x7e]*\Z/n.match(str) # for us-ascii
     end
-
     @encodings ||= Setting.repositories_encodings.split(',').collect(&:strip)
     @encodings.each do |encoding|
       begin
diff --git a/test/unit/helpers/repository_helper_test.rb b/test/unit/helpers/repository_helper_test.rb
index 457319a7..c5e66055 100644
--- a/test/unit/helpers/repository_helper_test.rb
+++ b/test/unit/helpers/repository_helper_test.rb
@@ -24,7 +24,7 @@ class RepositoryHelperTest < HelperTestCase
     with_settings :repositories_encodings => 'UTF-8,ISO-8859-1' do
       s1 = "Texte encod\xc3\xa9"
       s2 = "Texte encod\xe9"
-      s3 = s2
+      s3 = s2.dup
       if s1.respond_to?(:force_encoding)
         s1.force_encoding("UTF-8")
         s2.force_encoding("ASCII-8BIT")
@@ -39,7 +39,7 @@ class RepositoryHelperTest < HelperTestCase
     with_settings :repositories_encodings => 'UTF-8,EUC-JP' do
       s1 = "\xe3\x83\xac\xe3\x83\x83\xe3\x83\x89\xe3\x83\x9e\xe3\x82\xa4\xe3\x83\xb3"
       s2 = "\xa5\xec\xa5\xc3\xa5\xc9\xa5\xde\xa5\xa4\xa5\xf3"
-      s3 = s2
+      s3 = s2.dup
       if s1.respond_to?(:force_encoding)
         s1.force_encoding("UTF-8")
         s2.force_encoding("ASCII-8BIT")
@@ -54,7 +54,7 @@ class RepositoryHelperTest < HelperTestCase
     with_settings :repositories_encodings => 'ISO-8859-1' do
       s1 = "\xc3\x82\xc2\x80"
       s2 = "\xC2\x80"
-      s3 = s2
+      s3 = s2.dup
       if s1.respond_to?(:force_encoding)
         s1.force_encoding("UTF-8")
         s2.force_encoding("ASCII-8BIT")
@@ -64,5 +64,10 @@ class RepositoryHelperTest < HelperTestCase
       assert_equal s1, to_utf8(s3)
     end
   end
+
+  def test_to_utf8_blank_string
+    assert_equal "",  to_utf8("")
+    assert_equal nil, to_utf8(nil)
+  end
 end