diff --git a/pyro/mesh/patch.py b/pyro/mesh/patch.py
index 721bfc9d1..8a7f97164 100644
--- a/pyro/mesh/patch.py
+++ b/pyro/mesh/patch.py
@@ -245,15 +245,15 @@ class SphericalPolar(Grid2d):
     def __init__(self, nx, ny, *, ng=1,
                  xmin=0.2, xmax=1.0, ymin=0.0, ymax=1.0):
 
+        super().__init__(nx, ny, ng=ng, xmin=xmin, xmax=xmax, ymin=ymin, ymax=ymax)
+
         # Make sure theta is within [0, PI]
         assert ymin >= 0.0 and ymax <= np.pi, "y or \u03b8 should be within [0, \u03c0]."
 
         # Make sure the ghost cells doesn't extend out negative x(r)
-        assert xmin - ng*(xmax-xmin)/nx >= 0.0, \
+        assert xmin - ng*self.dx >= 0.0, \
             "xmin (r-direction), must be large enough so ghost cell doesn't have negative x."
 
-        super().__init__(nx, ny, ng=ng, xmin=xmin, xmax=xmax, ymin=ymin, ymax=ymax)
-
         self.coord_type = 1
 
         # Length of the side along r-direction, dr
diff --git a/pyro/simulation_null.py b/pyro/simulation_null.py
index c10fc75ce..0baaea658 100644
--- a/pyro/simulation_null.py
+++ b/pyro/simulation_null.py
@@ -1,4 +1,5 @@
 import h5py
+import numpy as np
 
 import pyro.mesh.boundary as bnd
 import pyro.util.profile_pyro as profile
@@ -52,6 +53,19 @@ def grid_setup(rp, ng=1):
                           ymin=ymin, ymax=ymax,
                           ng=ng)
 
+    # Make sure y-boundary condition is reflect when
+    # ymin = 0 and ymax = pi
+
+    if grid_type == "SphericalPolar":
+        if ymin <= 0.05:
+            rp.set_param("mesh.ylboundary", "reflect")
+            msg.warning("With SphericalPolar grid," +
+                        " mesh.ylboundary auto set to reflect when ymin ~ 0")
+        if abs(np.pi - ymax) <= 0.05:
+            rp.set_param("mesh.yrboundary", "reflect")
+            msg.warning("With SphericalPolar grid," +
+                        " mesh.yrboundary auto set to reflect when ymax ~ pi")
+
     return my_grid