diff --git a/baybe/parameters/base.py b/baybe/parameters/base.py
index d8ac2bdb2..c795b5812 100644
--- a/baybe/parameters/base.py
+++ b/baybe/parameters/base.py
@@ -33,7 +33,7 @@ class Parameter(ABC, SerialMixin):
     """Class variable encoding whether this parameter is discrete."""
 
     # object variables
-    name: str = field(validator=[instance_of(str), min_len(1)])
+    name: str = field(validator=(instance_of(str), min_len(1)))
     """The name of the parameter"""
 
     @abstractmethod
diff --git a/baybe/parameters/categorical.py b/baybe/parameters/categorical.py
index d26f8ed5c..8992ae27e 100644
--- a/baybe/parameters/categorical.py
+++ b/baybe/parameters/categorical.py
@@ -22,14 +22,13 @@ class CategoricalParameter(DiscreteParameter):
     # See base class.
 
     # object variables
-    # FIXME[typing]: https://github.com/python-attrs/attrs/issues/1197
     _values: Tuple[str, ...] = field(
         converter=tuple,
-        validator=[
+        validator=(
             min_len(2),
-            validate_unique_values,  # type: ignore
-            deep_iterable(member_validator=[instance_of(str), min_len(1)]),
-        ],
+            validate_unique_values,
+            deep_iterable(member_validator=(instance_of(str), min_len(1))),
+        ),
     )
     # See base class.
 
diff --git a/baybe/parameters/substance.py b/baybe/parameters/substance.py
index 3a21fec2a..f4f4e704b 100644
--- a/baybe/parameters/substance.py
+++ b/baybe/parameters/substance.py
@@ -46,7 +46,7 @@ class SubstanceParameter(DiscreteParameter):
     data: Dict[str, Smiles] = field(
         validator=deep_mapping(
             mapping_validator=min_len(2),
-            # TODO: Create cattrs issue for required `and_` and value/key_validator
+            # FIXME[typing]: https://github.com/python-attrs/attrs/issues/1206
             key_validator=and_(instance_of(str), min_len(1)),
             value_validator=lambda *x: None,
         )