diff --git a/test/json/json_encoding_test.rb b/test/json/json_encoding_test.rb
index be87f3c3d6..fba9ee2855 100644
--- a/test/json/json_encoding_test.rb
+++ b/test/json/json_encoding_test.rb
@@ -6,23 +6,14 @@ class JSONEncodingTest < Test::Unit::TestCase
 
   def setup
     @utf_8      = '"© ≠ €!"'
-    @ascii_8bit = @utf_8.dup.force_encoding('ascii-8bit')
+    @ascii_8bit = @utf_8.b
     @parsed     = "© ≠ €!"
     @generated  = '"\u00a9 \u2260 \u20ac!"'
-    if String.method_defined?(:encode)
-      @utf_16_data = @parsed.encode('utf-16be', 'utf-8')
-      @utf_16be = @utf_8.encode('utf-16be', 'utf-8')
-      @utf_16le = @utf_8.encode('utf-16le', 'utf-8')
-      @utf_32be = @utf_8.encode('utf-32be', 'utf-8')
-      @utf_32le = @utf_8.encode('utf-32le', 'utf-8')
-    else
-      require 'iconv'
-      @utf_16_data, = Iconv.iconv('utf-16be', 'utf-8', @parsed)
-      @utf_16be, = Iconv.iconv('utf-16be', 'utf-8', @utf_8)
-      @utf_16le, = Iconv.iconv('utf-16le', 'utf-8', @utf_8)
-      @utf_32be, = Iconv.iconv('utf-32be', 'utf-8', @utf_8)
-      @utf_32le, = Iconv.iconv('utf-32le', 'utf-8', @utf_8)
-    end
+    @utf_16_data = @parsed.encode(Encoding::UTF_16BE, Encoding::UTF_8)
+    @utf_16be = @utf_8.encode(Encoding::UTF_16BE, Encoding::UTF_8)
+    @utf_16le = @utf_8.encode(Encoding::UTF_16LE, Encoding::UTF_8)
+    @utf_32be = @utf_8.encode(Encoding::UTF_32BE, Encoding::UTF_8)
+    @utf_32le = @utf_8.encode(Encoding::UTF_32LE, Encoding::UTF_8)
   end
 
   def test_parse
diff --git a/test/json/json_generator_test.rb b/test/json/json_generator_test.rb
index d14966f8d0..37b28ab7b5 100755
--- a/test/json/json_generator_test.rb
+++ b/test/json/json_generator_test.rb
@@ -480,6 +480,6 @@ EOT
   end
 
   def test_nonutf8_encoding
-    assert_equal("\"5\u{b0}\"", "5\xb0".force_encoding("iso-8859-1").to_json)
+    assert_equal("\"5\u{b0}\"", "5\xb0".dup.force_encoding(Encoding::ISO_8859_1).to_json)
   end
 end
diff --git a/test/json/json_parser_test.rb b/test/json/json_parser_test.rb
index be9774891d..e04b0c93a5 100644
--- a/test/json/json_parser_test.rb
+++ b/test/json/json_parser_test.rb
@@ -502,7 +502,7 @@ EOT
   def test_parsing_frozen_ascii8bit_string
     assert_equal(
       { 'foo' => 'bar' },
-      JSON('{ "foo": "bar" }'.force_encoding(Encoding::ASCII_8BIT).freeze)
+      JSON('{ "foo": "bar" }'.b.freeze)
     )
   end