diff --git a/src/rstd/collections/tree/context.rs b/src/rstd/collections/tree/context.rs
index 71f547f..6cd509b 100644
--- a/src/rstd/collections/tree/context.rs
+++ b/src/rstd/collections/tree/context.rs
@@ -179,6 +179,10 @@ impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone, C: 'a + Comparator<A
     fn balancing_error<T: 'a>(&self, error: BalancingError) -> BTWrap<'a, Self, T> {
         Self::fail(error.into())
     }
+
+    fn node_heights(&self, node: &Self::Node) -> (u64, u64) {
+        (node.l.height, node.r.height)
+    }
 }
 
 impl<'a, Ctx: Context<'a>, A: Mentionable<'a, Ctx> + Clone, C: 'a + Comparator<A>, E: 'a>