diff --git a/.gitignore b/.gitignore
index b18192f..9eea669 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@
 /.yardoc
 /Gemfile.lock
 /gemfiles/*.lock
+/gemfiles/.bundle
 /_yardoc/
 /coverage/
 /doc/
diff --git a/gemfiles/rails_42.gemfile b/gemfiles/rails_42.gemfile
index 6a5d7d1..8f81710 100644
--- a/gemfiles/rails_42.gemfile
+++ b/gemfiles/rails_42.gemfile
@@ -6,6 +6,7 @@ gem "actionpack", "~> 4.2"
 gem "railties", "~> 4.2"
 
 group :development do
+  gem "appraisal", "~> 2.2"
   gem "pry", "~> 0.10.1"
   gem "pry-byebug", "~> 3.2.0"
   gem "sdoc", "~> 0.4.1"
diff --git a/gemfiles/rails_50.gemfile b/gemfiles/rails_50.gemfile
index e944c26..a929f66 100644
--- a/gemfiles/rails_50.gemfile
+++ b/gemfiles/rails_50.gemfile
@@ -6,6 +6,7 @@ gem "actionpack", "~> 5.0"
 gem "railties", "~> 5.0"
 
 group :development do
+  gem "appraisal", "~> 2.2"
   gem "pry", "~> 0.10.1"
   gem "pry-byebug", "~> 3.2.0"
   gem "sdoc", "~> 0.4.1"
diff --git a/gemfiles/rails_51.gemfile b/gemfiles/rails_51.gemfile
index 3af389a..9b4e1ad 100644
--- a/gemfiles/rails_51.gemfile
+++ b/gemfiles/rails_51.gemfile
@@ -6,6 +6,7 @@ gem "actionpack", "~> 5.1"
 gem "railties", "~> 5.1"
 
 group :development do
+  gem "appraisal", "~> 2.2"
   gem "pry", "~> 0.10.1"
   gem "pry-byebug", "~> 3.2.0"
   gem "sdoc", "~> 0.4.1"