diff --git a/execjs.gemspec b/execjs.gemspec
index e83912b..3a6c9be 100644
--- a/execjs.gemspec
+++ b/execjs.gemspec
@@ -19,4 +19,5 @@ Gem::Specification.new do |s|
   s.email   = ["sstephenson@gmail.com", "josh@joshpeek.com"]
 
   s.required_ruby_version = '>= 2.5.0'
+  s.add_dependency 'json', '>= 2'
 end
diff --git a/lib/execjs/external_runtime.rb b/lib/execjs/external_runtime.rb
index a0325f4..ce35194 100644
--- a/lib/execjs/external_runtime.rb
+++ b/lib/execjs/external_runtime.rb
@@ -19,7 +19,7 @@ def eval(source, options = {})
         source = source.encode(Encoding::UTF_8)
 
         if /\S/ =~ source
-          exec("return eval(#{::JSON.generate("(#{source})", quirks_mode: true)})")
+          exec("return eval(#{::JSON.generate("(#{source})")})")
         end
       end
 
@@ -66,7 +66,7 @@ def write_to_tempfile(contents)
         end
 
         def extract_result(output, filename)
-          status, value, stack = output.empty? ? [] : ::JSON.parse(output, create_additions: false)
+          status, value, stack = output.empty? ? [] : ::JSON.parse(output)
           if status == "ok"
             value
           else
@@ -156,7 +156,7 @@ def json2_source
 
       def encode_source(source)
         encoded_source = encode_unicode_codepoints(source)
-        ::JSON.generate("(function(){ #{encoded_source} })()", quirks_mode: true)
+        ::JSON.generate("(function(){ #{encoded_source} })()")
       end
 
       def encode_unicode_codepoints(str)
diff --git a/lib/execjs/ruby_rhino_runtime.rb b/lib/execjs/ruby_rhino_runtime.rb
index 4829263..ff7edc4 100644
--- a/lib/execjs/ruby_rhino_runtime.rb
+++ b/lib/execjs/ruby_rhino_runtime.rb
@@ -35,7 +35,7 @@ def eval(source, options = {})
       def call(properties, *args)
         # Might no longer be necessary if therubyrhino handles Symbols directly:
         # https://github.com/rubyjs/therubyrhino/issues/43
-        converted_args = JSON.parse(JSON.generate(args), create_additions: false)
+        converted_args = JSON.parse(JSON.generate(args))
 
         unbox @rhino_context.eval(properties).call(*converted_args)
       rescue Exception => e
diff --git a/test/test_execjs.rb b/test/test_execjs.rb
index b3fec92..2c2d7af 100644
--- a/test/test_execjs.rb
+++ b/test/test_execjs.rb
@@ -152,10 +152,10 @@ def test_context_call_missing_function
     { "a" => 1, "b" => [2, 3]},
     { "a" => true }
   ].each_with_index do |value, index|
-    json_value = JSON.generate(value, quirks_mode: true)
+    json_value = JSON.generate(value)
 
     define_method("test_json_value_#{index}") do
-      assert_output value, JSON.parse(json_value, quirks_mode: true)
+      assert_output value, JSON.parse(json_value)
     end
 
     define_method("test_exec_value_#{index}") do