diff --git a/pyvisgraph/visible_vertices.py b/pyvisgraph/visible_vertices.py
index f1415d6..f2470e2 100644
--- a/pyvisgraph/visible_vertices.py
+++ b/pyvisgraph/visible_vertices.py
@@ -28,7 +28,7 @@
 INF = 10000
 """Due to floating point representation error, some functions need to
    truncate floating point numbers to a certain tolerance."""
-COLIN_TOLERANCE = 13
+COLIN_TOLERANCE = 10
 T = 10**COLIN_TOLERANCE
 T2 = 10.0**COLIN_TOLERANCE