diff --git a/src/crystal_ball.scad b/src/crystal_ball.scad
index 4caf1952..37e78be5 100644
--- a/src/crystal_ball.scad
+++ b/src/crystal_ball.scad
@@ -24,8 +24,9 @@ module crystal_ball(radius, theta = 360, phi = 180) {
         $fn = __nearest_multiple_of_4(frags)
     );
 
-    // _hole_r = 0.0005 for avoiding warnings
-    _hole_r = 0.0005;
+    // _hole_r = 0.0005 for avoiding warnings when using 2015.03
+    // I downloaded 2017.01.20 and found that the problem is solved.
+    _hole_r = version_num() >= 20170120 ? 0 : 0.0005;
     ring_extrude(
         shape_pts, 
         angle = theta, 
@@ -34,7 +35,6 @@ module crystal_ball(radius, theta = 360, phi = 180) {
     );
 
     // hook for testing
-
     test_crystal_ball_pie(shape_pts);
 }