diff --git a/aoc.cabal b/aoc.cabal
index 5dd464e..4d766a5 100644
--- a/aoc.cabal
+++ b/aoc.cabal
@@ -29,6 +29,7 @@ executable aoc
         bytestring,
         colour,
         containers,
+        deepseq,
         directory,
         exceptions,
         extra,