diff --git a/generateTagClusters.py b/generateTagClusters.py
index 5bd769e..9c32318 100644
--- a/generateTagClusters.py
+++ b/generateTagClusters.py
@@ -1266,7 +1266,10 @@ def add_edge(edges, edge_points, coords, i, j):
         # Semiperimeter of triangle
         s = (a + b + c)/2.0
         # Area of triangle by Heron's formula
-        area = math.sqrt(s*(s-a)*(s-b)*(s-c))
+        try:
+            area = math.sqrt(s*(s-a)*(s-b)*(s-c))
+        except ValueError:
+            return False
         if area == 0:
             return False
         circum_r = a*b*c/(4.0*area)