diff --git a/lib/acme/client/resources/challenges/base.rb b/lib/acme/client/resources/challenges/base.rb
index 3044ec8..c9fa508 100644
--- a/lib/acme/client/resources/challenges/base.rb
+++ b/lib/acme/client/resources/challenges/base.rb
@@ -8,6 +8,10 @@ def initialize(client, **arguments)
     assign_attributes(arguments)
   end
 
+  def [](key)
+    to_h[key]
+  end
+
   def challenge_type
     self.class::CHALLENGE_TYPE
   end