interface is not a protocol

gistfile1.txt

https://github.com/wilkes/karras/blob/6a8297fe79615fe3188af7388757214088492cbd/src/karras/core.clj#L34

(defprotocol MongoMappable
"(to-dbo [d])
(to-clj [d])
Implementations provided for Map, List, Object, and nil"
(to-dbo [d])
(to-clj [d])
(to-description [d]))



<my code>

(extend DateTime
   MongoMappable
   (:to-dbo [d] (str d))
   (:to-clj [d] (str d))
   (:to-description [d] (str d)))

<error>

Unknown location:
  error: java.lang.IllegalArgumentException: interface karras.core.MongoMappable is not a protocol

Compilation failed.