diff --git a/lib/vagrant-cachier/bucket.rb b/lib/vagrant-cachier/bucket.rb
index 74ee0c5..377e2cd 100644
--- a/lib/vagrant-cachier/bucket.rb
+++ b/lib/vagrant-cachier/bucket.rb
@@ -8,7 +8,7 @@ module VagrantPlugins
 
       def self.auto_detect(env)
         @buckets.each do |bucket|
-          if env[:machine].guest.capability?(bucket.capability)
+          if bucket.respond_to?(:capability) && env[:machine].guest.capability?(bucket.capability)
             env[:machine].config.cache.enable bucket.bucket_name
           end
         end