diff --git a/lib/puma/acme/structs.rb b/lib/puma/acme/structs.rb
index 0b4ca8e..ef87af2 100644
--- a/lib/puma/acme/structs.rb
+++ b/lib/puma/acme/structs.rb
@@ -68,7 +68,7 @@ def names
       end
 
       def expired?(now: Time.now.utc)
-        x509.not_after > now
+        x509.not_after < now
       end
 
       def usable?(now: Time.now.utc)
@@ -135,7 +135,7 @@ def self.from(acme_order)
       end
 
       def expired?(now: Time.now.utc)
-        not_after > now
+        expires < now
       end
     end
   end