diff --git a/wraith.gemspec b/wraith.gemspec
index 9e29800d..072c302c 100644
--- a/wraith.gemspec
+++ b/wraith.gemspec
@@ -20,6 +20,7 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency 'pry'
   spec.add_development_dependency 'rspec'
+  spec.add_development_dependency 'casperjs'
 
   spec.add_runtime_dependency 'rake'
   spec.add_runtime_dependency 'image_size'