diff --git a/prototype/Doubt/Cofree.swift b/prototype/Doubt/Cofree.swift
index c81955c74..0704a779e 100644
--- a/prototype/Doubt/Cofree.swift
+++ b/prototype/Doubt/Cofree.swift
@@ -79,4 +79,13 @@ public func == <A: Equatable, B: Equatable> (left: Cofree<A, B>, right: Cofree<A
 }
 
 
+// MARK: - Hashing
+
+extension Cofree {
+	public func hash(annotation annotation: B -> Hash, leaf: A -> Hash) -> Hash {
+		return .Ordered([ annotation(extract), unwrap.hash(ifLeaf: leaf, ifRecur: { $0.hash(annotation: annotation, leaf: leaf) }) ])
+	}
+}
+
+
 import Prelude