diff --git a/src/TernaryGraph.purs b/src/TernaryGraph.purs
index e7a15c2..009ba5c 100644
--- a/src/TernaryGraph.purs
+++ b/src/TernaryGraph.purs
@@ -1,6 +1,6 @@
 module TernaryGraph where
 
-import Prelude ( discard, class Monoid, class Semigroup, Unit, ($), (<<<), (<>), (*), (+), (-), (/))
+import Prelude (discard, class Monoid, class Semigroup, Unit, ($), (<=), (<<<), (<>), (*), (+), (-), (/))
 
 import Data.Array ((!!), concat, cons, mapWithIndex, range)
 import Data.Functor (map)