diff --git a/masque/shapes/poly_collection.py b/masque/shapes/poly_collection.py
index afa9c99..73aca30 100644
--- a/masque/shapes/poly_collection.py
+++ b/masque/shapes/poly_collection.py
@@ -56,6 +56,8 @@ class PolyCollection(Shape):
         """
         Iterator which provides slices which index vertex_lists
         """
+        if self._vertex_offsets.size == 0:
+            return
         for ii, ff in zip(
                 self._vertex_offsets,
                 chain(self._vertex_offsets, (self._vertex_lists.shape[0],)),
@@ -168,7 +170,9 @@ class PolyCollection(Shape):
             annotations = copy.deepcopy(self.annotations),
             ) for vv in self.polygon_vertices]
 
-    def get_bounds_single(self) -> NDArray[numpy.float64]:         # TODO note shape get_bounds doesn't include repetition
+    def get_bounds_single(self) -> NDArray[numpy.float64] | None:         # TODO note shape get_bounds doesn't include repetition
+        if self._vertex_lists.size == 0:
+            return None
         return numpy.vstack((numpy.min(self._vertex_lists, axis=0),
                              numpy.max(self._vertex_lists, axis=0)))