diff --git a/common.mk b/common.mk
index fd14ab6..28f2bcf 100644
--- a/common.mk
+++ b/common.mk
@@ -36,7 +36,7 @@ UNICODE_DATA_HEADERS = \
 RUBY_RELEASE_DATE = $(RUBY_RELEASE_YEAR)-$(RUBY_RELEASE_MONTH)-$(RUBY_RELEASE_DAY)
 RUBYLIB       = $(PATH_SEPARATOR)
 RUBYOPT       = -
-RUN_OPTS      = --disable-gems
+RUN_OPTS      = --disable-gems -I$(srcdir)/../json-2.3.0/lib
 
 GITPULLOPTIONS = --rebase
 
@@ -1026,8 +1026,7 @@ srcs-ext: $(EXT_SRCS)
 realclean-srcs-ext::
 	$(Q)$(RM) $(EXT_SRCS)
 
-EXTRA_SRCS = $(srcdir)/ext/json/parser/parser.c \
-	     $(srcdir)/ext/date/zonetab.h \
+EXTRA_SRCS = $(srcdir)/ext/date/zonetab.h \
 	     $(empty)
 
 srcs-extra: $(EXTRA_SRCS)
@@ -1140,11 +1139,6 @@ $(srcdir)/ext/ripper/ripper.c: $(srcdir)/ext/ripper/tools/preproc.rb $(srcdir)/p
 		Q=$(Q) ECHO=$(ECHO) RM="$(RM)" BISON=$(YACC) top_srcdir=../.. srcdir=. VPATH="$${VPATH}" \
 		RUBY="$(BASERUBY)" PATH_SEPARATOR="$(PATH_SEPARATOR)"
 
-$(srcdir)/ext/json/parser/parser.c: $(srcdir)/ext/json/parser/parser.rl $(srcdir)/ext/json/parser/prereq.mk
-	$(ECHO) generating $@
-	$(Q) $(CHDIR) $(@D) && $(exec) $(MAKE) -f prereq.mk $(mflags) \
-		Q=$(Q) ECHO=$(ECHO) top_srcdir=../../.. srcdir=. VPATH=../../.. BASERUBY="$(BASERUBY)"
-
 $(srcdir)/ext/date/zonetab.h: $(srcdir)/ext/date/zonetab.list $(srcdir)/ext/date/prereq.mk
 	$(ECHO) generating $@
 	$(Q) $(CHDIR) $(@D) && $(exec) $(MAKE) -f prereq.mk $(mflags) \
diff --git a/ext/.document b/ext/.document
index 6a49157..97e5120 100644
--- a/ext/.document
+++ b/ext/.document
@@ -27,9 +27,6 @@ gdbm/gdbm.c
 io/console/console.c
 io/nonblock/nonblock.c
 io/wait/wait.c
-json/generator/generator.c
-json/lib
-json/parser/parser.c
 nkf/lib
 nkf/nkf.c
 objspace/objspace.c
diff --git a/gems/bundled_gems b/gems/bundled_gems
index ce2dd1b..69ae0ae 100644
--- a/gems/bundled_gems
+++ b/gems/bundled_gems
@@ -4,3 +4,4 @@ power_assert 1.1.7 https://github.com/k-tsj/power_assert
 rake 13.0.1 https://github.com/ruby/rake
 test-unit 3.3.4 https://github.com/test-unit/test-unit
 xmlrpc 0.3.0 https://github.com/ruby/xmlrpc
+json 2.3.0 https://github.com/flori/json
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index 69f03ae..2011334 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -214,7 +214,6 @@ class TestModule < Test::Unit::TestCase
 
     ancestors = Object.ancestors
     mixins = ancestors - [Object, Kernel, BasicObject]
-    mixins << JSON::Ext::Generator::GeneratorMethods::String if defined?(JSON::Ext::Generator::GeneratorMethods::String)
     assert_equal([Object, Kernel, BasicObject], ancestors - mixins)
     assert_equal([String, Comparable, Object, Kernel, BasicObject], String.ancestors - mixins)
   end
@@ -467,7 +466,6 @@ class TestModule < Test::Unit::TestCase
     assert_equal([Mixin], User.included_modules)
 
     mixins = Object.included_modules - [Kernel]
-    mixins << JSON::Ext::Generator::GeneratorMethods::String if defined?(JSON::Ext::Generator::GeneratorMethods::String)
     assert_equal([Kernel], Object.included_modules - mixins)
     assert_equal([Comparable, Kernel], String.included_modules - mixins)
   end