diff --git a/cameo/area.c b/cameo/area.c
index 364f4a5..322f892 100644
--- a/cameo/area.c
+++ b/cameo/area.c
@@ -167,9 +167,8 @@ static int hit_segment(double fx, double fy, double tx, double ty,
 	dx = b->x-a->x;
 	dy = b->y-a->y;
 
-	if (enter && dy < 0)
-		return 0;
-	if (!enter && dy > 0)
+	/* -dy becomes the x component of the normal vector */
+	if (enter ? dy < 0 : dy > 0)
 		return 0;
 
 	d = hypot(dx, dy);