diff --git a/geomagio/algorithm/SqDistAlgorithm.py b/geomagio/algorithm/SqDistAlgorithm.py
index d79383de83a98dd9d4ba08d5592cbfba6a5bf504..169aad38a25ac2cf0540e4b5be79309cac0e7a03 100644
--- a/geomagio/algorithm/SqDistAlgorithm.py
+++ b/geomagio/algorithm/SqDistAlgorithm.py
@@ -328,6 +328,8 @@ class SqDistAlgorithm(Algorithm):
         # set some default values
         if l0 is None:
             l = np.nanmean(yobs[0:int(m)])
+            if l is np.nan:
+                l = 0.
         else:
             l = l0
             if not np.isscalar(l0):
@@ -487,7 +489,7 @@ class SqDistAlgorithm(Algorithm):
 
         r = np.cumsum(r)
         l = l + r[-1]
-        s = list(np.array(s) - np.hstack((r, np.tile(r[-1], m - 1))))
+        s = np.array(s) - np.hstack((r, np.tile(r[-1], m - 1)))
 
         return (yhat[:len(yobs) + fc],
                 s[:len(yobs) + fc],