diff --git a/masque/shapes/shape.py b/masque/shapes/shape.py
index 1cf2846..43aa222 100644
--- a/masque/shapes/shape.py
+++ b/masque/shapes/shape.py
@@ -74,7 +74,7 @@ class Shape(Positionable, Rotatable, FlippableImpl, Copyable, Scalable,
         pass
 
     @abstractmethod
-    def normalized_form(self, norm_value: int) -> normalized_shape_tuple:
+    def normalized_form(self, norm_value: float) -> normalized_shape_tuple:
         """
         Writes the shape in a standardized notation, with offset, scale, and rotation
          information separated out from the remaining values.