diff --git a/src/p63.hy b/src/p63.hy
index 445e61d..076600e 100644
--- a/src/p63.hy
+++ b/src/p63.hy
@@ -1,4 +1,5 @@
 ; Note: mostly solved using algebra
+(require hyrule [->])
 (import math)
 
 (-> (lfor n (range 1 10)