diff --git a/labelme/utils/qt.py b/labelme/utils/qt.py
index e20016e1fe791c758d46d0e348317b309206c72a..5a70c8351cf8ad3476d698ad7bfea766cb90b851 100644
--- a/labelme/utils/qt.py
+++ b/labelme/utils/qt.py
@@ -90,6 +90,8 @@ def distancetoline(point, line):
         return np.linalg.norm(p3 - p1)
     if np.dot((p3 - p2), (p1 - p2)) < 0:
         return np.linalg.norm(p3 - p2)
+    if np.linalg.norm(p2 - p1) == 0:
+        return 0
     return np.linalg.norm(np.cross(p2 - p1, p1 - p3)) / np.linalg.norm(p2 - p1)