diff -Nur ruby-2.4.0.orig/common.mk ruby-2.4.0/common.mk
--- ruby-2.4.0.orig/common.mk	2016-11-30 14:29:19.000000000 -0300
+++ ruby-2.4.0/common.mk	2017-01-11 14:30:02.197544090 -0300
@@ -27,7 +27,7 @@
 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-1.8.1/lib
 
 INCFLAGS = -I. -I$(arch_hdrdir) -I$(hdrdir) -I$(srcdir) -I$(UNICODE_HDR_DIR)
 
@@ -814,8 +814,7 @@
 
 srcs-ext: $(EXT_SRCS)
 
-srcs-extra: $(srcdir)/ext/json/parser/parser.c \
-	    $(srcdir)/ext/date/zonetab.h \
+srcs-extra: $(srcdir)/ext/date/zonetab.h \
 	    $(empty)
 
 LIB_SRCS = $(srcdir)/lib/unicode_normalize/tables.rb
@@ -911,11 +910,6 @@
 		Q=$(Q) ECHO=$(ECHO) RM="$(RM)" top_srcdir=../.. srcdir=. VPATH="$(PWD)" \
 		RUBY="$(BASERUBY)" PATH_SEPARATOR="$(PATH_SEPARATOR)"
 
-$(srcdir)/ext/json/parser/parser.c: $(srcdir)/ext/json/parser/parser.rl
-	$(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
 	$(ECHO) generating $@
 	$(Q) $(CHDIR) $(@D) && $(exec) $(MAKE) -f prereq.mk $(MFLAGS) \
diff -Nur ruby-2.4.0.orig/ext/.document ruby-2.4.0/ext/.document
--- ruby-2.4.0.orig/ext/.document	2014-08-02 11:55:36.000000000 -0300
+++ ruby-2.4.0/ext/.document	2017-01-11 14:25:50.386510205 -0300
@@ -35,9 +35,6 @@
 io/nonblock/nonblock.c
 io/wait/lib
 io/wait/wait.c
-json/ext/generator/generator.c
-json/ext/parser/parser.c
-json/lib
 mathn/complex/complex.c
 mathn/rational/rational.c
 nkf/lib
diff -Nur ruby-2.4.0.orig/gems/bundled_gems ruby-2.4.0/gems/bundled_gems
--- ruby-2.4.0.orig/gems/bundled_gems	2016-12-22 00:53:53.000000000 -0300
+++ ruby-2.4.0/gems/bundled_gems	2017-01-11 14:28:18.729284682 -0300
@@ -5,3 +5,4 @@
 rake 12.0.0
 test-unit 3.2.3
 xmlrpc 0.2.1
+json 1.8.1
diff -Nur ruby-2.4.0.orig/test/ruby/test_module.rb ruby-2.4.0/test/ruby/test_module.rb
--- ruby-2.4.0.orig/test/ruby/test_module.rb	2016-11-14 16:27:24.000000000 -0300
+++ ruby-2.4.0/test/ruby/test_module.rb	2017-01-11 14:25:50.386510205 -0300
@@ -211,7 +211,6 @@
 
     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
@@ -449,7 +448,6 @@
     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