diff --git a/WorkloadManagementSystem/Utilities/PilotCStoJSONSynchronizer.py b/WorkloadManagementSystem/Utilities/PilotCStoJSONSynchronizer.py
index b188714cbff..3e97eeb8e94 100644
--- a/WorkloadManagementSystem/Utilities/PilotCStoJSONSynchronizer.py
+++ b/WorkloadManagementSystem/Utilities/PilotCStoJSONSynchronizer.py
@@ -183,9 +183,12 @@ def _getDNs(self, certGroupName):
       usersString = gConfig.getValue('/Registry/Groups/' + certGroupName + '/Users')
       usersInGroup = usersString.split(',')
       DNs = [gConfig.getValue('/Registry/Users/' + user + '/DN') for user in usersInGroup]
-      return S_OK(DNs)
-    except AttributeError:
-      return S_ERROR('Some error occured while getting the DNs.')
+      if (DNs == [None]):
+        return S_ERROR('Users in this group don`t have DN ')
+      else:
+        return S_OK(DNs)
+    except AttributeError as ae:
+      gLogger.exception("Error occured while getting the DNs", lException=ae)
 
   def _getPilotOptionsPerSetup(self, setup, pilotDict):
     """ Given a setup, returns its pilot options in a dictionary
diff --git a/WorkloadManagementSystem/Utilities/test/Test_PilotCStoJSONSynchronizer.py b/WorkloadManagementSystem/Utilities/test/Test_PilotCStoJSONSynchronizer.py
index 3387bfd6361..eec9e0a2801 100644
--- a/WorkloadManagementSystem/Utilities/test/Test_PilotCStoJSONSynchronizer.py
+++ b/WorkloadManagementSystem/Utilities/test/Test_PilotCStoJSONSynchronizer.py
@@ -29,6 +29,13 @@ def setUp(self):
         }
       }
     }
+    Resources
+    {
+      Sites
+      {
+
+      }
+    }
     Systems
     {
       WorkloadManagement
@@ -69,6 +76,10 @@ def setUp(self):
           CA = /DC=ch/DC=voodo/CN=Voodo Grid Certification Authority
           Email = franek.bolek@voodo.pl
         }
+        Nemo
+        {
+
+        }
       }
       Groups
       {
@@ -83,6 +94,14 @@ def setUp(self):
           #@@-ggg@diracAdmin - 2015-07-07 13:40:55
           VO = lhcb
         }
+        Empty_group
+        {
+
+        }
+        Nautilus
+        {
+         Users=Nemo
+        }
       }
     }
     '''
@@ -129,6 +148,16 @@ def test_failure(self):
     res = synchroniser._getDNs('nonExistingGroup')
     self.assertFalse(res['OK'])
 
+  def test_empty_group(self):
+    synchronizer = PilotCStoJSONSynchronizer()
+    res = synchronizer._getDNs('Empty')
+    self.assertFalse(res['OK'])
+
+  def test_user_without_DN(self):
+    synchronizer = PilotCStoJSONSynchronizer()
+    res = synchronizer._getDNs('Nautilus')
+    self.assertFalse(res['OK'])
+
 
 if __name__ == '__main__':
   suite = unittest.defaultTestLoader.loadTestsFromTestCase(PilotCStoJSONSynchronizerTestCase)