diff --git a/library/cadbiom/models/clause_constraints/mcl/CLUnfolder.py b/library/cadbiom/models/clause_constraints/mcl/CLUnfolder.py
index a37c5d15557684637047606ac95abab6788d64f4..efc9fe6e95d79183b80d538c18c056a66209a479 100644
--- a/library/cadbiom/models/clause_constraints/mcl/CLUnfolder.py
+++ b/library/cadbiom/models/clause_constraints/mcl/CLUnfolder.py
@@ -154,9 +154,11 @@ shift():
 
 """
 from __future__ import print_function
+from packaging import version
 
 #from pyCryptoMS import CryptoMS
 from pycryptosat import Solver as CryptoMS
+from pycryptosat import __version__ as solver_version
 from cadbiom.models.biosignal.translators.gt_visitors import compile_cond, compile_event
 from cadbiom.models.clause_constraints.CLDynSys import Clause, Literal
 from cadbiom.models.clause_constraints.mcl.MCLSolutions import RawSolution, MCLException
@@ -439,10 +441,10 @@ class CLUnfolder(object):
         """Disable solver statistics (never used)"""
         self.__stats = False
 
-    def _stats(self):
+    def stats(self):
         """Display solver statistics"""
-        print("\n NB Variables in solver:", self.__nb_vars)
-        print("NB Clauses in solver:", self.__nb_clauses)
+        LOGGER.info("NB Variables in solver:", self.__nb_vars)
+        LOGGER.info("NB Clauses in solver:", self.__nb_clauses)
 
     def set_include_aux_clauses(self, val):
         """Flag to include auxiliary clause to eliminate undesirable solutions.
@@ -1375,6 +1377,24 @@ class CLUnfolder(object):
             LOGGER.debug(str(self.__initial_constraints))
 
 
+    def __sync_stats(self, solver):
+        """Sync local data (nb vars, nb clauses) with solver state
+        if stats are activated (never besides in test environment).
+
+        .. note:: Its the only way to set __nb_vars and __nb_clauses attributes.
+        """
+        if version.parse(solver_version) < version.parse("5.6.9"):
+            if solver.nb_vars() > self.__nb_vars:
+                self.__nb_vars = solver.nb_vars()
+        else:
+            if solver.nb_vars > self.__nb_vars:
+                self.__nb_vars = solver.nb_vars
+            # Starting from pycryptosat 5.2, nb_clauses is private
+            # Starting from 5.6.9 the attribute is exposed
+            if solver.nb_clauses > self.__nb_clauses:
+                self.__nb_clauses = solver.nb_clauses
+
+
     def __constraints_satisfied(self):
         """Ask the SAT solver if the query/system is satisfiable in the given
         number of steps.
@@ -1391,13 +1411,9 @@ class CLUnfolder(object):
 
         if self.__stats:
             # If stats are activated (never besides in test environment):
-            # sync local data (nb vars, nb clauses with solver state)
-            if solver.nb_vars() > self.__nb_vars:
-                self.__nb_vars = solver.nb_vars()
+            # sync local data (nb vars, nb clauses) with solver state
+            self.__sync_stats(solver)
 
-            # Starting from pycryptosat 5.2, nb_clauses() is a private attribute
-            #if solver.nb_clauses() > self.__nb_clauses:
-            #    self.__nb_clauses = solver.nb_clauses()
         # Is the problem satisfiable ?
         return solver.is_satisfiable()
 
@@ -1422,12 +1438,8 @@ class CLUnfolder(object):
 
         if self.__stats:
             # If stats are activated (never besides in test environment):
-            # sync local data (nb vars, nb clauses with solver state)
-            if solver.nb_vars() > self.__nb_vars:
-                self.__nb_vars = solver.nb_vars()
-            # Starting from pycryptosat 5.2, nb_clauses() is a private attribute
-            #if solver.nb_clauses() > self.__nb_clauses:
-            #    self.__nb_clauses = solver.nb_clauses()
+            # sync local data (nb vars, nb clauses) with solver state
+            self.__sync_stats(solver)
 
         if LOGGER.getEffectiveLevel() == DEBUG:
             LOGGER.debug("__msolve_constraints :: vvars : %s", vvars)