diff --git a/day4/default.nix b/day4/default.nix
index 7d6bcb7..1492878 100644
--- a/day4/default.nix
+++ b/day4/default.nix
@@ -13,7 +13,7 @@ let
       (listRange matrix)));
   construct_diags = matrix: construct_diags' (map reverseList matrix);
   diags_1 = map concatStrings (construct_diags grid);
-  diags_2 = map concatStrings (construct_diags' (grid));
+  diags_2 = map concatStrings (construct_diags' grid);
 in {
   part1 =
     listSumWith (s: (length (matchAll "XMAS" s)) + (length (matchAll "SAMX" s)))