diff --git a/narwhals/dtypes.py b/narwhals/dtypes.py
index 8ef5d30183..b433bd6fd5 100644
--- a/narwhals/dtypes.py
+++ b/narwhals/dtypes.py
@@ -633,9 +633,9 @@ def __init__(self, categories: Iterable[str] | type[enum.Enum]) -> None:
     @property
     def categories(self) -> tuple[str, ...]:
         """The categories in the dataset."""
-        if cached := self._cached_categories:
+        if (cached := self._cached_categories) is not None:
             return cached
-        if delayed := self._delayed_categories:
+        if (delayed := self._delayed_categories) is not None:
             self._cached_categories = delayed.to_tuple()
             return self._cached_categories
         msg = f"Internal structure of {type(self).__name__!r} is invalid."  # pragma: no cover
diff --git a/tests/dtypes/dtypes_test.py b/tests/dtypes/dtypes_test.py
index 8c6eb7f6c4..7fb5cc29f2 100644
--- a/tests/dtypes/dtypes_test.py
+++ b/tests/dtypes/dtypes_test.py
@@ -441,7 +441,9 @@ def test_cast_decimal_to_native() -> None:
             )
 
 
-@pytest.mark.parametrize("categories", [["a", "b"], enum.Enum("Test", "a b"), [1, 2, 3]])
+@pytest.mark.parametrize(
+    "categories", [["a", "b"], enum.Enum("Test", "a b"), [1, 2, 3], []]
+)
 def test_enum_valid(categories: Iterable[Any] | type[enum.Enum]) -> None:
     dtype = nw.Enum(categories)
     assert dtype == nw.Enum