diff --git a/src/tools.c b/src/tools.c
index 0ef58d4..35f4043 100644
--- a/src/tools.c
+++ b/src/tools.c
@@ -12,7 +12,7 @@ int
 length(int x1, int y1, int x2, int y2)
 {
 	const int dist_x = abs(x1 - x2);
-	const int dist_y = abs(y1 - y1);
+	const int dist_y = abs(y1 - y2);
 	const float dist = sqrt(dist_x * dist_x + dist_y * dist_y);
 	return dist;
 }