diff --git a/lib/rack/crawler_detect.rb b/lib/rack/crawler_detect.rb
index b19f29a..522ed47 100644
--- a/lib/rack/crawler_detect.rb
+++ b/lib/rack/crawler_detect.rb
@@ -8,11 +8,11 @@ class CrawlerDetect
     def initialize(app, options = {})
       Rack::Request::Helpers.module_eval do
         def is_crawler?
-          env["rack.crawler_detect"][:is_crawler]
+          !!(env["rack.crawler_detect"] && env["rack.crawler_detect"][:is_crawler])
         end
 
         def crawler_name
-          env["rack.crawler_detect"][:crawler_name]
+          env["rack.crawler_detect"] && env["rack.crawler_detect"][:crawler_name]
         end
       end
       @app = app