diff --git a/cirq-core/cirq/protocols/json_serialization.py b/cirq-core/cirq/protocols/json_serialization.py
index 45ac308d32f..45fcb6856f0 100644
--- a/cirq-core/cirq/protocols/json_serialization.py
+++ b/cirq-core/cirq/protocols/json_serialization.py
@@ -256,6 +256,7 @@ def default(self, o):
                 sympy.StrictLessThan,
                 sympy.Equality,
                 sympy.Unequality,
+                sympy.Xor,
             ),
         ):
             return {'cirq_type': f'sympy.{o.__class__.__name__}', 'args': o.args}