diff --git a/Gemfile b/Gemfile
index 94dad75..40eb150 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,3 +3,4 @@ source "https://rubygems.org"
 gem "rake"
 gem "jsonschema"
 gem "watchr"
+gem "json", :platforms => [:ruby_18]
diff --git a/Gemfile.lock b/Gemfile.lock
index f407f49..150206b 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,6 +1,7 @@
 GEM
   remote: https://rubygems.org/
   specs:
+    json (1.8.0)
     jsonschema (2.0.2)
     rake (10.0.4)
     watchr (0.7)
@@ -9,6 +10,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  json
   jsonschema
   rake
   watchr