diff --git a/da/sf6/statevector.py b/da/sf6/statevector.py
index 22dae948c592204553c3b083a85a1f6ebdf3a361..f62fdbf5d291fbc92ca5da2b34a2f6bcfa2c97ee 100755
--- a/da/sf6/statevector.py
+++ b/da/sf6/statevector.py
@@ -130,7 +130,7 @@ class SF6StateVector(StateVector):
         for k in self.speciesdict.keys(): 
             logging.debug("   ->    %s" % k)
 
-    def propagate(self):
+    def propagate(self,dummy):
         """ 
         :rtype: None
 
@@ -143,7 +143,7 @@ class SF6StateVector(StateVector):
         """
 
         self.ensemble_members.append([])
-        cov = self.get_covariance(None)
+        cov = self.get_covariance(None,None)
         newmean = np.ones(self.nparams)*0.15    #WP
         self.make_new_ensemble(self.nlag+1, newmean = newmean, covariancematrix=cov)
         self.ensemble_members.pop(0)