1 files changed, 1 insertions, 1 deletions
diff --git a/Day4.cs b/Day4.cs
index 5a453e0..b6b2c91 100644
--- a/Day4.cs
+++ b/Day4.cs
@@ -2,7 +2,7 @@
 
 namespace aoc2019
 {
-    internal class Day4 : Day
+    internal sealed class Day4 : Day
     {
         public override int DayNumber => 4;