diff --git a/prody/dynamics/clustenm.py b/prody/dynamics/clustenm.py
index 9bac6ea92..7583bc431 100644
--- a/prody/dynamics/clustenm.py
+++ b/prody/dynamics/clustenm.py
@@ -1076,7 +1076,7 @@ def run(self, cutoff=15., n_modes=3, gamma=1., n_confs=50, rmsd=1.0,
         self._sparse = kwargs.get('sparse', False)
         self._kdtree = kwargs.get('kdtree', False)
         self._turbo = kwargs.get('turbo', False)
-        self._nproc = kwargs.pop('nproc', None)
+        self._nproc = kwargs.pop('nproc', 0)
         if kwargs.get('zeros', False):
             LOGGER.warn('ClustENM cannot use zero modes so ignoring this kwarg')