diff --git a/masque/shapes/arc.py b/masque/shapes/arc.py
index aaceeb5..53fadb8 100644
--- a/masque/shapes/arc.py
+++ b/masque/shapes/arc.py
@@ -218,6 +218,7 @@ class Arc(PositionableImpl, Shape):
             rotation: float,
             annotations: annotations_t = None,
             repetition: Repetition | None = None,
+            angle_ref: ArcAngleRef | str = ArcAngleRef.Center,
             ) -> 'Arc':
         new = cls.__new__(cls)
         new._radii = radii