diff --git a/tool/gem-unpack.rb b/tool/gem-unpack.rb
index 6fb80d3bbe..cb05719463 100644
--- a/tool/gem-unpack.rb
+++ b/tool/gem-unpack.rb
@@ -1,3 +1,4 @@
+require 'fileutils'
 require 'rubygems'
 require 'rubygems/package'