diff --git a/src/day05/Day05.kt b/src/day05/Day05.kt
index fa6f46e..f792482 100644
--- a/src/day05/Day05.kt
+++ b/src/day05/Day05.kt
@@ -48,7 +48,7 @@ fun readVector(input: String): Vector {
 }
 
 fun findOverlaps(input: List<Vector>): Int {
-    var points: MutableMap<Point, Int> = mutableMapOf()
+    val points: MutableMap<Point, Int> = mutableMapOf()
     input
         .flatMap { it.points }
         .forEach { points[it] = 1 + points.getOrDefault(it, 0) }