diff --git a/curve_simplify.py b/curve_simplify.py
index 5cc0623267c41921f878fa7aae8c7846fe33b9ee..70e9f82558eb8f0a8d53f6bec677ca6c3eb4b79c 100644
--- a/curve_simplify.py
+++ b/curve_simplify.py
@@ -142,6 +142,9 @@ def altitude(point1, point2, pointn):
     if edge2.length == 0:
         altitude = 0
         return altitude
+    if edge1.length == 0:
+        altitude = edge2.length
+        return altitude
     alpha = edge1.angle(edge2)
     altitude = math.sin(alpha) * edge2.length
     return altitude