diff --git a/tuskarclient/common/utils.py b/tuskarclient/common/utils.py
index 9e28145..b951a46 100644
--- a/tuskarclient/common/utils.py
+++ b/tuskarclient/common/utils.py
@@ -88,6 +88,26 @@ def find_resource(manager, name_or_id):
         raise exc.CommandError(msg)
 
 
+def marshal_association(args, resource_dict, assoc_name):
+    """Marshal resource association into an API request dict.
+
+    Distinguish between 3 cases:
+
+    - when the value in args is present, set the value in dict too,
+    - when the value in args is an empty string, set the value in dict
+      to none,
+    - when the value in args is None, it means the user did not specify
+      it on the command line and it should not be present in the dict
+      (important for update).
+    """
+    assoc_value = getattr(args, assoc_name, None)
+    if assoc_value == '':
+        resource_dict[assoc_name] = None
+    elif assoc_value:
+        # TODO(jistr): support for selecting resources by name
+        resource_dict[assoc_name] = {'id': assoc_value}
+
+
 def string_to_bool(arg):
     return arg.strip().lower() in ('t', 'true', 'yes', '1')
 
diff --git a/tuskarclient/tests/common/test_utils.py b/tuskarclient/tests/common/test_utils.py
index ed2c4c1..474eb4d 100644
--- a/tuskarclient/tests/common/test_utils.py
+++ b/tuskarclient/tests/common/test_utils.py
@@ -46,3 +46,26 @@ class DefineCommandsTest(test_utils.TestCase):
         dummy.do_dummy_list = do_dummy_list
         dummy.other_method = mock.Mock('other_method', return_value=43)
         return dummy
+
+
+class MarshalAssociationTest(test_utils.TestCase):
+
+    def setUp(self):
+        super(MarshalAssociationTest, self).setUp()
+        self.args = mock.Mock(spec=['rack'])
+        self.dict = {}
+
+    def test_with_id(self):
+        self.args.rack = '10'
+        utils.marshal_association(self.args, self.dict, 'rack')
+        self.assertEqual(self.dict['rack']['id'], '10')
+
+    def test_with_empty_association(self):
+        self.args.rack = ''
+        utils.marshal_association(self.args, self.dict, 'rack')
+        self.assertEqual(self.dict['rack'], None)
+
+    def test_when_unset(self):
+        self.args.rack = None
+        utils.marshal_association(self.args, self.dict, 'rack')
+        self.assertFalse('rack' in self.dict)