diff --git a/hmms/cthmm.pyx b/hmms/cthmm.pyx
index 06667b9..c2c4559 100755
--- a/hmms/cthmm.pyx
+++ b/hmms/cthmm.pyx
@@ -739,7 +739,7 @@ cdef class CtHMM(hmm.HMM):
 
         for it in range( iterations ):
 
-            print("it",it)
+            # print("it",it)
 
             self._prepare_matrices_pt( t_seqs )
 
@@ -814,23 +814,18 @@ cdef class CtHMM(hmm.HMM):
 
                         if i == j:
 
-                            tA /= self._pt[ ix ]
+                            tA = numpy.divide(tA, self._pt[ ix ], out=numpy.zeros_like(tA), where=tA!=0)
                             tau[i]  += numpy.exp( self.log_sum( (ksi_sum[ix] + numpy.log( tA ) ).flatten() ) )   #tau is not in log prob anymore.
 
                         else:
                             tA *= self._q[i,j]
-                            tA /= self._pt[ ix ]
+                            tA = numpy.divide(tA, self._pt[ ix ], out=numpy.zeros_like(tA), where=tA!=0)
                             eta[i,j] += numpy.exp( self.log_sum( (ksi_sum[ix] + numpy.log( tA ) ).flatten() ) )  #eta is not in log prob anymore.
 
             #Update parameter Q:
-
             self._q = ( eta.T / tau ).T
 
             self._q = numpy.nan_to_num(self._q)   # nan can appear, when some of the states is not reachable
-
-            if sum( self._q.flatten() ) == 0:
-                raise ValueError("Parameter error! Matrix Q can't contain unreachable states.")
-
             for i in range( s_num ):
                 self._q[i,i] = - numpy.sum( self._q[i,:] )
 
@@ -934,8 +929,7 @@ cdef class CtHMM(hmm.HMM):
 
         for it in range( iterations ):
 
-            print("iteration ", i+1, "/", iterations )
-
+            # print("iteration ", it+1, "/", iterations )
 
             self._prepare_matrices_pt( times )
 
@@ -1033,14 +1027,15 @@ cdef class CtHMM(hmm.HMM):
 
                         if i == j:
 
-                            tA /= self._pt[ ix ]
+                            tA = numpy.divide(tA, self._pt[ ix ], out=numpy.zeros_like(tA), where=tA!=0)
 
                             tau[i]  += numpy.exp( self.log_sum( (ksi_sum[ix] + numpy.log( tA ) ).flatten() ) )   #tau is not in log prob anymore.
 
 
                         else:
                             tA *= self._q[i,j]
-                            tA /= self._pt[ ix ]
+                            tA = numpy.divide(tA, self._pt[ ix ], out=numpy.zeros_like(tA), where=tA!=0)
+
                             eta[i,j] += numpy.exp( self.log_sum( (ksi_sum[ix] + numpy.log( tA ) ).flatten() ) )  #eta is not in log prob anymore.
 
             #Update parameters:
@@ -1052,13 +1047,8 @@ cdef class CtHMM(hmm.HMM):
             #jump rates matrice
             self._q = ( eta.T / tau ).T
 
-
-
             self._q = numpy.nan_to_num(self._q)   # nan can appear, when some of the states is not reachable
 
-            if sum( self._q.flatten() ) == 0:
-                raise ValueError("Parameter error! Matrix Q can't contain unreachable states.")
-
             for i in range( s_num ):
                 self._q[i,i] = - numpy.sum( self._q[i,:] )