diff --git a/TurTLE/DNS.py b/TurTLE/DNS.py
index cd1bb79b968bb3855af32ccc05b90dddd7f5fb37..b8e4bd15ba1365db9bbca1a8f68ec6d8c50913e3 100644
--- a/TurTLE/DNS.py
+++ b/TurTLE/DNS.py
@@ -654,7 +654,7 @@ class DNS(_code):
         parser_NSVEp_extra = subparsers.add_parser(
                 'NSVEp_extra_sampling',
                 help = 'plain Navier-Stokes vorticity formulation, with basic fluid tracers, that sample velocity gradient, as well as pressure and its derivatives.')
-        for parser in [
+        for pp in [
                 'NSVE',
                 'NSVE_no_output',
                 'NSVEparticles_no_output',
@@ -663,23 +663,23 @@ class DNS(_code):
                 'NSVEp_extra',
                 'static_field',
                 'kraichnan_field']:
-            eval('self.simulation_parser_arguments({0})'.format('parser_' + parser))
-            eval('self.job_parser_arguments({0})'.format('parser_' + parser))
-            eval('self.parameters_to_parser_arguments({0})'.format('parser_' + parser))
+            eval('self.simulation_parser_arguments({0})'.format('parser_' + pp))
+            eval('self.job_parser_arguments({0})'.format('parser_' + pp))
+            eval('self.parameters_to_parser_arguments({0})'.format('parser_' + pp))
             eval('self.parameters_to_parser_arguments('
                     'parser_{0},'
-                    'self.generate_extra_parameters(\'{0}\'))'.format(parser))
-        for parser in [
+                    'self.generate_extra_parameters(\'{0}\'))'.format(pp))
+        for pp in [
                 'NSVEparticles_no_output',
                 'NSVEp2',
                 'NSVEp2p',
                 'NSVEp_extra',
                 'static_field',
                 'kraichnan_field']:
-            eval('self.particle_parser_arguments({0})'.format('parser_' + parser))
+            eval('self.particle_parser_arguments({0})'.format('parser_' + pp))
             eval('self.parameters_to_parser_arguments('
                     'parser_{0},'
-                    'self.NSVEp_extra_parameters)'.format(parser))
+                    'self.NSVEp_extra_parameters)'.format(pp))
         return None
     def generate_extra_parameters(
             self,
@@ -1033,6 +1033,8 @@ class DNS(_code):
         # take care of fields' initial condition
         # first, check if initial field exists
         need_field = False
+        if self.check_current_vorticity_exists:
+            need_field = True
         if self.dns_type in [
                 'NSVE',
                 'NSVE_no_output',