diff --git a/trilegal/doc/resolvedstellarpops.io.rst b/trilegal/doc/resolvedstellarpops.io.rst
diff --git a/trilegal/doc/resolvedstellarpops.match.rst b/trilegal/doc/resolvedstellarpops.match.rst
diff --git a/trilegal/doc/resolvedstellarpops.math.mpfit.rst b/trilegal/doc/resolvedstellarpops.math.mpfit.rst
diff --git a/trilegal/doc/resolvedstellarpops.math.rst b/trilegal/doc/resolvedstellarpops.math.rst
diff --git a/trilegal/doc/resolvedstellarpops.rst b/trilegal/doc/resolvedstellarpops.rst
diff --git a/trilegal/doc/resolvedstellarpops.tools.rst b/trilegal/doc/resolvedstellarpops.tools.rst
diff --git a/trilegal/doc/resolvedstellarpops.trilegal.rst b/trilegal/doc/resolvedstellarpops.trilegal.rst
diff --git a/trilegal/isochrones.py b/trilegal/isochrones.py
diff --git a/trilegal/tracks.py b/trilegal/tracks.py
diff --git a/trilegal/utils.py b/trilegal/utils.py
diff --git a/trilegal_model_grid.py b/trilegal_model_grid.py
diff --git a/utils/utils.py b/utils/utils.py
@@ -46,8 +46,11 @@ def count_uncert_ratio(numerator, denominator):
     ''' combine poisson error to calculate ratio uncertainty'''
     n = float(numerator)
     d = float(denominator)
-    return (n / d) * (1./np.sqrt(n) + 1./np.sqrt(d))
-
+    try:
+        cur = (n / d) * (1./np.sqrt(n) + 1./np.sqrt(d))
+    except ZeroDivisionError:
+        cur = np.nan
+    return cur
 
 def points_inside_poly(points, all_verts):
     """ Proxy to the correct way with mpl """