diff --git a/lib/fluent/config/types.rb b/lib/fluent/config/types.rb
index a8739f9d15..4f5df084a4 100644
--- a/lib/fluent/config/types.rb
+++ b/lib/fluent/config/types.rb
@@ -64,7 +64,7 @@ def self.bool_value(str)
       end
     end
 
-    STRING_TYPE = Proc.new { |val, opts| val.to_s.encode(Encoding::UTF_8) }
+    STRING_TYPE = Proc.new { |val, opts| val.to_s.force_encoding(Encoding::UTF_8) }
     ENUM_TYPE = Proc.new { |val, opts|
       s = val.to_sym
       list = opts[:list]
@@ -85,7 +85,7 @@ def self.bool_value(str)
         value
       else
         case type
-        when :string  then value.to_s.encode(Encoding::UTF_8)
+        when :string  then value.to_s.force_encoding(Encoding::UTF_8)
         when :integer then value.to_i
         when :float   then value.to_f
         when :size then Config.size_value(value)
diff --git a/test/config/test_types.rb b/test/config/test_types.rb
index 350b7b32c7..6c12418bd7 100644
--- a/test/config/test_types.rb
+++ b/test/config/test_types.rb
@@ -69,6 +69,17 @@ class TestConfigTypes < ::Test::Unit::TestCase
       assert_equal Encoding::UTF_8, Config::STRING_TYPE.call('test', {}).encoding
     end
 
+    data('latin' => 'Märch',
+         'ascii' => 'ascii',
+         'space' => '     ',
+         'number' => '1',
+         'Hiragana' => 'あいうえお')
+    test 'string w/ binary' do |str|
+      actual = Config::STRING_TYPE.call(str.b, {})
+      assert_equal str, actual
+      assert_equal Encoding::UTF_8, actual.encoding
+    end
+
     test 'enum' do
       assert_equal :val, Config::ENUM_TYPE.call('val', {list: [:val, :value, :v]})
       assert_equal :v, Config::ENUM_TYPE.call('v', {list: [:val, :value, :v]})
@@ -143,6 +154,14 @@ class TestConfigTypes < ::Test::Unit::TestCase
       assert_raise(RuntimeError.new("unknown type in REFORMAT: foo")){ Config::HASH_TYPE.call("x:1,y:2", {value_type: :foo}) }
     end
 
+    data('latin' => ['3:Märch', {"3"=>"Märch"}],
+         'ascii' => ['ascii:ascii', {"ascii"=>"ascii"}],
+         'number' => ['number:1', {"number"=>"1"}],
+         'Hiragana' => ['hiragana:あいうえお', {"hiragana"=>"あいうえお"}])
+    test 'hash w/ binary' do |(target, expected)|
+      assert_equal(expected, Config::HASH_TYPE.call(target.b, { value_type: :string }))
+    end
+
     test 'array' do
       assert_equal(["1","2",1], Config::ARRAY_TYPE.call('["1","2",1]', {}))
       assert_equal(["1","2","1"], Config::ARRAY_TYPE.call('1,2,1', {}))