diff --git a/t4_devkit/schema/tables/object_ann.py b/t4_devkit/schema/tables/object_ann.py
index 19557fe..455d6b0 100644
--- a/t4_devkit/schema/tables/object_ann.py
+++ b/t4_devkit/schema/tables/object_ann.py
@@ -45,7 +45,7 @@ def decode(self) -> NDArrayU8:
         """
         counts = base64.b64decode(self.counts)
         data = {"counts": counts, "size": self.size}
-        return cocomask.decode(data).T
+        return cocomask.decode(data)
 
 
 @dataclass
diff --git a/t4_devkit/tier4.py b/t4_devkit/tier4.py
index 1bdfffa..9f53b8b 100644
--- a/t4_devkit/tier4.py
+++ b/t4_devkit/tier4.py
@@ -11,14 +11,22 @@
 
 from t4_devkit.common.geometry import is_box_in_image, view_points
 from t4_devkit.common.timestamp import sec2us, us2sec
-from t4_devkit.dataclass import Box2D, Box3D, LidarPointCloud, RadarPointCloud, Shape, ShapeType
+from t4_devkit.dataclass import (
+    Box2D,
+    Box3D,
+    LidarPointCloud,
+    RadarPointCloud,
+    SemanticLabel,
+    Shape,
+    ShapeType,
+)
 from t4_devkit.schema import SchemaName, SensorModality, VisibilityLevel, build_schema
 from t4_devkit.viewer import Tier4Viewer, distance_color, format_entity
 
 if TYPE_CHECKING:
     from t4_devkit.typing import CamIntrinsicType, NDArrayF64, NDArrayU8, VelocityType
 
-    from .dataclass import BoxType, SemanticLabel
+    from .dataclass import BoxType
     from .schema import (
         Attribute,
         CalibratedSensor,