diff --git a/Gemfile.lock b/Gemfile.lock
index b68989a..1f83b5a 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -2,6 +2,7 @@ PATH
   remote: .
   specs:
     perf_check (0.10.5)
+      bundler
       colorize
       diffy
       rake
@@ -17,20 +18,20 @@ GEM
     pry (0.12.2)
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
-    rake (12.3.2)
-    rspec (3.8.0)
-      rspec-core (~> 3.8.0)
-      rspec-expectations (~> 3.8.0)
-      rspec-mocks (~> 3.8.0)
-    rspec-core (3.8.2)
-      rspec-support (~> 3.8.0)
-    rspec-expectations (3.8.4)
+    rake (13.0.1)
+    rspec (3.9.0)
+      rspec-core (~> 3.9.0)
+      rspec-expectations (~> 3.9.0)
+      rspec-mocks (~> 3.9.0)
+    rspec-core (3.9.0)
+      rspec-support (~> 3.9.0)
+    rspec-expectations (3.9.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-mocks (3.8.1)
+      rspec-support (~> 3.9.0)
+    rspec-mocks (3.9.0)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-support (3.8.2)
+      rspec-support (~> 3.9.0)
+    rspec-support (3.9.0)
 
 PLATFORMS
   ruby
@@ -41,4 +42,4 @@ DEPENDENCIES
   rspec
 
 BUNDLED WITH
-   1.17.2
+   1.17.3
diff --git a/bin/perf_check b/bin/perf_check
index 52a19be..4dee8f9 100755
--- a/bin/perf_check
+++ b/bin/perf_check
@@ -1,6 +1,11 @@
 #!/usr/bin/env ruby
 
-require 'perf_check'
+begin
+  require 'perf_check'
+rescue LoadError
+  $LOAD_PATH.unshift(File.expand_path('../lib', __dir__))
+  retry
+end
 
 app_root =
   begin
diff --git a/lib/perf_check.rb b/lib/perf_check.rb
index 0b995ef..2acdf60 100644
--- a/lib/perf_check.rb
+++ b/lib/perf_check.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'benchmark'
 require 'bundler'
 require 'colorize'
@@ -7,6 +9,7 @@
 require 'net/http'
 require 'open3'
 require 'ostruct'
+require 'securerandom'
 
 class PerfCheck
   autoload :VERSION, 'perf_check/version'
@@ -89,9 +92,12 @@ def run
   def bundle
     Bundler.with_clean_env do
       execute(
+        { 'BUNDLE_APP_CONFIG' => bundle_app_config_path },
         'bundle', 'install', '--frozen', '--retry', '3', '--jobs', '3',
         fail_with: BundleError
       )
+    ensure
+      FileUtils.rm_rf(File.join(app_root, bundle_app_config_path))
     end
   end
 
@@ -105,6 +111,12 @@ def execute(*args, fail_with: nil)
 
   private
 
+  # Returns a random bundle config path so we don't clobber any settings
+  # previously made in a working directory.
+  def bundle_app_config_path
+    @bundle_app_config_path ||= ".bundle-#{SecureRandom.uuid}"
+  end
+
   def logger_level
     options.verbose ? Logger::DEBUG : Logger::INFO
   end
@@ -200,8 +212,10 @@ def cleanup_and_report
     callbacks = {}
 
     if $!
-      callbacks[:error_message] = "#{$!.class}: #{$!.message}\n"
-      callbacks[:error_message] << $!.backtrace.map{|x| "\t#{x}"}.join("\n")
+      callbacks[:error_message] = +"#{$!.class}: #{$!.message}\n"
+      callbacks[:error_message] << $!.backtrace.map do |line|
+        "\t#{line}"
+      end.join("\n")
     end
 
     trigger_when_finished_callbacks(callbacks)
diff --git a/lib/perf_check/version.rb b/lib/perf_check/version.rb
index 0410efc..c7783d7 100644
--- a/lib/perf_check/version.rb
+++ b/lib/perf_check/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 class PerfCheck
-  VERSION = '0.10.5'
+  VERSION = '0.10.5' unless defined?(VERSION)
 end
diff --git a/perf_check b/perf_check
new file mode 120000
index 0000000..b4a6c3b
--- /dev/null
+++ b/perf_check
@@ -0,0 +1 @@
+/Users/manfred/Code/perf_check
\ No newline at end of file
diff --git a/perf_check.gemspec b/perf_check.gemspec
index de45303..e197baa 100644
--- a/perf_check.gemspec
+++ b/perf_check.gemspec
@@ -10,8 +10,9 @@ Gem::Specification.new do |s|
   s.homepage = 'https://github.com/rubytune/perf_check'
   s.license = 'MIT'
 
-  s.add_development_dependency 'rspec'
   s.add_development_dependency 'pry'
+  s.add_development_dependency 'rspec'
+  s.add_runtime_dependency 'bundler'
   s.add_runtime_dependency 'colorize'
   s.add_runtime_dependency 'diffy'
   s.add_runtime_dependency 'rake'
diff --git a/spec/bundles/rails-4.tar.bz2 b/spec/bundles/rails-4.tar.bz2
index 6e1773a..3fbbf1b 100644
Binary files a/spec/bundles/rails-4.tar.bz2 and b/spec/bundles/rails-4.tar.bz2 differ
diff --git a/spec/bundles/rails-5.tar.bz2 b/spec/bundles/rails-5.tar.bz2
index dea97a3..b512751 100644
Binary files a/spec/bundles/rails-5.tar.bz2 and b/spec/bundles/rails-5.tar.bz2 differ
diff --git a/spec/support/apps.rb b/spec/support/apps.rb
index 40c08cc..fddc721 100644
--- a/spec/support/apps.rb
+++ b/spec/support/apps.rb
@@ -55,9 +55,7 @@ def link_perf_check
     end
 
     def run_bundle_install
-      # Use the --frozen option to prevent the test suite from writing a new
-      # Gemfile.lock.
-      bundle 'install', '--frozen', '--retry', '3', '--jobs', '3'
+      PerfCheck.new(Dir.pwd).bundle
     end
 
     def run_db_setup