diff --git a/tiramisu/option/baseoption.py b/tiramisu/option/baseoption.py
index 23e9776..33c68bb 100644
--- a/tiramisu/option/baseoption.py
+++ b/tiramisu/option/baseoption.py
@@ -70,10 +70,17 @@ class Base:
             properties = frozenset()
         elif isinstance(properties, tuple):
             properties = frozenset(properties)
-        if is_multi and 'empty' not in properties:
-            # if option is a multi, it cannot be "empty" (None not allowed in the list)
-            # "empty" is removed for follower's option
-            properties = properties | {'empty'}
+        if is_multi:
+            # if option is a multi, it cannot be 'empty' (None not allowed in the list) and cannot have multiple time the same value
+            # 'empty' and 'unique' are removed for follower's option
+            if 'notunique' in properties:
+                properties = properties - {'notunique'}
+            else:
+                properties = properties | {'unique'}
+            if 'notempty' in properties:
+                properties = properties - {'notempty'}
+            else:
+                properties = properties | {'empty'}
         assert isinstance(properties, frozenset), _('invalid properties type {0} for {1},'
                                                     ' must be a frozenset').format(type(properties),
                                                                                    name)