diff --git a/lib/big_tuna/runner.rb b/lib/big_tuna/runner.rb
index 513541d..3627e97 100644
--- a/lib/big_tuna/runner.rb
+++ b/lib/big_tuna/runner.rb
@@ -3,7 +3,7 @@ class Runner
     def self.execute(dir, command)
       end_command = "cd #{dir} && #{command}"
       BigTuna.logger.debug("Executing: #{end_command}")
-      with_clean_env do
+      with_clean_env(dir) do
         output = Output.new(dir, command)
         buffer = []
         status = Open4.popen4(end_command) do |_, _, stdout, stderr|
@@ -18,13 +18,20 @@ def self.execute(dir, command)
       end
     end
 
-    def self.with_clean_env
+    def self.with_clean_env(dir)
       Bundler.with_clean_env do
         begin
           rails_env = ENV.delete("RAILS_ENV")
+          old_bundle_gemfile = nil
+          bundle_gemfile = File.join(dir, "Gemfile")
+          if File.file?(bundle_gemfile)
+            old_bundle_gemfile = ENV.delete("BUNDLE_GEMFILE")
+            ENV["BUNDLE_GEMFILE"] = bundle_gemfile
+          end
           yield
         ensure
           ENV["RAILS_ENV"] = rails_env if rails_env # if nil, then don't set any key
+          ENV["BUNDLE_GEMFILE"] = old_bundle_gemfile if old_bundle_gemfile
         end
       end
     end
diff --git a/test/unit/bundler_project_test.rb b/test/unit/bundler_project_test.rb
new file mode 100644
index 0000000..301fae7
--- /dev/null
+++ b/test/unit/bundler_project_test.rb
@@ -0,0 +1,43 @@
+require 'test_helper'
+
+class BundlerProjectTest < ActiveSupport::TestCase
+  def setup
+    super
+    create_bundler_test_repo
+  end
+
+  def teardown
+    destroy_test_repo
+    super
+  end
+
+  test "bundler projects are auto-discovered" do
+    project = project_with_steps({:name => "bundlerproject", :vcs_source => "test/files/bundler_repo", :vcs_type => "git"}, "env")
+    project.build!
+    run_delayed_jobs()
+    build = project.recent_build
+    envs = build.parts[0].output[0].stdout
+    bundle_gemfile_env = envs.map! { |e| e.split("=") }.assoc("BUNDLE_GEMFILE")
+    assert_equal File.join(build.build_dir, "Gemfile"), bundle_gemfile_env[1]
+  end
+
+  private
+  def create_bundler_test_repo
+    command = <<-CMD.gsub("\n", "; ")
+      mkdir -p test/files/bundler_repo
+      cd test/files/bundler_repo
+      git init
+      git config user.name git
+      git config user.email git@example.com
+      echo "my file" > file
+      touch Gemfile
+      git add file Gemfile
+      git commit -m "bundler project added"
+    CMD
+    `#{command}`
+  end
+
+  def destroy_test_repo
+    FileUtils.rm_rf 'test/files/bundler_repo'
+  end
+end