diff --git a/lib/pp.gemspec b/lib/pp.gemspec
index e77be442de..f3f3527086 100644
--- a/lib/pp.gemspec
+++ b/lib/pp.gemspec
@@ -19,4 +19,6 @@ Gem::Specification.new do |spec|
   spec.bindir        = "exe"
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
+
+  spec.add_dependency "prettyprint"
 end