diff --git a/internal/2021/register.go b/internal/2021/register.go
index 272321e..967767b 100644
--- a/internal/2021/register.go
+++ b/internal/2021/register.go
@@ -1,6 +1,7 @@
 package year2021
 
 import (
+	_ "advent-of-code/internal/2021/DayFour"
 	_ "advent-of-code/internal/2021/DayOne"
 	_ "advent-of-code/internal/2021/DayThree"
 	_ "advent-of-code/internal/2021/DayTwo"