diff --git a/Main.hs b/Main.hs
index 8f70fa1..cd481a8 100644
--- a/Main.hs
+++ b/Main.hs
@@ -5,6 +5,7 @@
 {-# LANGUAGE OverloadedStrings #-}
 
 import           Control.Applicative
+import           Control.Category.Structures
 import           Control.Lens
 import           Control.Lens.SemiIso
 import           Control.SIArrow