diff --git a/src/flow/comparator.rs b/src/flow/comparator.rs
index 493e9f8..c7c2a6c 100644
--- a/src/flow/comparator.rs
+++ b/src/flow/comparator.rs
@@ -33,3 +33,16 @@ impl<A: PartialOrd> Comparator<A> for DefaultComparator {
         }
     }
 }
+
+pub struct RcComparator<C>(C);
+
+mod rc_comparator_impl {
+    use super::*;
+    use std::rc::Rc;
+
+    impl<A, C: Comparator<A>> Comparator<Rc<A>> for RcComparator<C> {
+        fn pick_smaller(&self, kl: &Rc<A>, kr: &Rc<A>) -> Comparison {
+            self.0.pick_smaller(kl, kr)
+        }
+    }
+}