Index: ../trunk-jpl/src/m/classes/stochasticforcing.py
===================================================================
--- ../trunk-jpl/src/m/classes/stochasticforcing.py	(revision 26854)
+++ ../trunk-jpl/src/m/classes/stochasticforcing.py	(revision 26855)
@@ -156,12 +156,13 @@
 
     def marshall(self, prefix, md, fid):  # {{{
         yts = md.constants.yts
-        num_fields = len(self.fields)
 
         WriteData(fid, prefix, 'object', self, 'fieldname', 'isstochasticforcing', 'format', 'Boolean')
         if not self.isstochasticforcing:
             return md
+
         else:
+            num_fields = len(self.fields)
             # Retrieve dimensionality of each field
             dimensions = self.defaultdimension * np.ones((num_fields))
             for ind, field in enumerate(self.fields):