diff --git a/.ruby-version b/.ruby-version
new file mode 100644
index 0000000..197c4d5
--- /dev/null
+++ b/.ruby-version
@@ -0,0 +1 @@
+2.4.0
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index e17f8b3..6a46964 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -7,6 +7,7 @@
   Coveralls.wear!
 else
   # coco : local code coverage
+  require 'fileutils'
   require 'coco'
 end