diff --git a/contrail_api_cli/exceptions.py b/contrail_api_cli/exceptions.py
index e23a2ca..7a9f95c 100644
--- a/contrail_api_cli/exceptions.py
+++ b/contrail_api_cli/exceptions.py
@@ -81,3 +81,9 @@ class BackRefsExists(Exists):
 
     def __str__(self):
         return "Back references from %s exists" % self._paths
+
+
+class IsSystemResource(Exists):
+
+    def __str__(self):
+        return "System resources %s cannot be changed" % self._paths
diff --git a/contrail_api_cli/resource.py b/contrail_api_cli/resource.py
index e107aec..b6713d2 100644
--- a/contrail_api_cli/resource.py
+++ b/contrail_api_cli/resource.py
@@ -20,7 +20,7 @@
 
 from .utils import FQName, Path, Observable, to_json
 from .exceptions import ResourceNotFound, ResourceMissing, \
-    CollectionNotFound, ChildrenExists, BackRefsExists
+    CollectionNotFound, ChildrenExists, BackRefsExists, IsSystemResource
 from .context import Context
 
 
@@ -56,23 +56,27 @@ def wrapper(self, *args, **kwargs):
                     raise CollectionNotFound(collection=self)
             elif e.http_status == 409:
                 # contrail 3.2
-                matches = re.match(r'^Delete when children still present: (\[[^]]*\])', e.message)
+                matches = re.match(r'^Delete when children still present: (\[[^]]*\])($| \(HTTP 409\)$)', e.message)
                 if matches:
                     raise ChildrenExists(
                         resources=list(hrefs_list_to_resources(matches.group(1))))
-                matches = re.match(r'^Delete when resource still referred: (\[[^]]*\])', e.message)
+                matches = re.match(r'^Delete when resource still referred: (\[[^]]*\])($| \(HTTP 409\)$)', e.message)
                 if matches:
                     raise BackRefsExists(
                         resources=list(hrefs_list_to_resources(matches.group(1))))
                 # contrail 2.21
-                matches = re.match(r'^Children (.*) still exist$', e.message)
+                matches = re.match(r'^Children (.*) still exist($| \(HTTP 409\)$)', e.message)
                 if matches:
                     raise ChildrenExists(
                         resources=list(hrefs_to_resources(matches.group(1))))
-                matches = re.match(r'^Back-References from (.*) still exist$', e.message)
+                matches = re.match(r'^Back-References from (.*) still exist($| \(HTTP 409\)$)', e.message)
                 if matches:
                     raise BackRefsExists(
                         resources=list(hrefs_to_resources(matches.group(1))))
+                # contrail 5.1
+                matches = re.match(r'^Cannot modify system resource (.*) .*\(([a-f0-9]{8}-?[a-f0-9]{4}-?4[a-f0-9]{3}-?[89ab][a-f0-9]{3}-?[a-f0-9]{12})\)($| \(HTTP 409\)$)', e.message)
+                if matches:
+                    raise IsSystemResource(resources=[Resource(matches.group(1), uuid=matches.group(2))])
             raise
     return wrapper
 
diff --git a/contrail_api_cli/tests/test_resource.py b/contrail_api_cli/tests/test_resource.py
index b6832b8..92acc14 100644
--- a/contrail_api_cli/tests/test_resource.py
+++ b/contrail_api_cli/tests/test_resource.py
@@ -11,7 +11,7 @@
 from contrail_api_cli.utils import Path, FQName
 from contrail_api_cli.resource import RootCollection, Collection, Resource, ResourceEncoder
 from contrail_api_cli.client import ContrailAPISession
-from contrail_api_cli.exceptions import ResourceNotFound, ResourceMissing, CollectionNotFound
+from contrail_api_cli.exceptions import ResourceNotFound, ResourceMissing, CollectionNotFound, ChildrenExists, BackRefsExists, IsSystemResource
 
 from .utils import CLITest
 
@@ -560,6 +560,22 @@ def test_resource_comparaison(self, mock_session):
                     r1, r1.fq_name, r2, r2.fq_name, is_equal),
             )
 
+    @mock.patch('contrail_api_cli.resource.Context.session')
+    def test_exist_exception(self, mock_session):
+        r = Resource('foo', uuid='ec1afeaa-8930-43b0-a60a-939f23a50724')
+        test_suite = [
+            ("Delete when children still present: %s" % ['http://host%s' % r.path], ChildrenExists),
+            ("Children http://host%s still exist" % r.path, ChildrenExists),
+            ("Delete when resource still referred: %s" % ['http://host%s' % r.path], BackRefsExists),
+            ("Back-References from http://host%s still exist" % r.path, BackRefsExists),
+            ("Cannot modify system resource %s %s(%s)" % (r.type, r.fq_name, r.uuid), IsSystemResource),
+        ]
+        for msg, exception in test_suite:
+            mock_session.get_json.side_effect = HttpError(http_status=409, message=msg)
+            with self.assertRaises(exception) as e:
+                r.fetch()
+                self.assertListEqual([r], e.exception.resources)
+
 
 if __name__ == "__main__":
     unittest.main()