diff --git a/dfs.tidal b/dfs.tidal
index 1addc62..fdeb72f 100644
--- a/dfs.tidal
+++ b/dfs.tidal
@@ -4,6 +4,8 @@ import Data.Graph.Inductive.Basic
 
 import Data.Array
 
+import Data.List
+
 import qualified Data.Array as A
 
 tabulate :: Bounds -> [Vertex] -> Table Int