diff --git a/masque/repetition.py b/masque/repetition.py
index a774f7e..20ec0a3 100644
--- a/masque/repetition.py
+++ b/masque/repetition.py
@@ -350,7 +350,7 @@ class Arbitrary(Repetition):
         return (f'<Arbitrary {len(self.displacements)}pts >')
 
     def __eq__(self, other: Any) -> bool:
-        if not type(other) is not type(self):
+        if type(other) is not type(self):
             return False
         return numpy.array_equal(self.displacements, other.displacements)