diff --git a/cirq-google/cirq_google/api/v2/run_context.proto b/cirq-google/cirq_google/api/v2/run_context.proto
index e0cf0a27fa3..e3722cb652a 100644
--- a/cirq-google/cirq_google/api/v2/run_context.proto
+++ b/cirq-google/cirq_google/api/v2/run_context.proto
@@ -90,11 +90,11 @@ message DeviceParameter {
     repeated string path = 1;
 
     // If the value is an array, the index of the array to change.
-    int64 idx = 2;
+    optional int64 idx = 2;
 
     // String representation of the units, if any.
     // Examples: "GHz", "ns", etc.
-    string units = 3;
+    optional string units = 3;
 
     // Note that the device parameter values will be populated
     // by the sweep values themselves.
diff --git a/cirq-google/cirq_google/api/v2/run_context_pb2.py b/cirq-google/cirq_google/api/v2/run_context_pb2.py
index 7d62e40f33a..ac1fbe25102 100644
--- a/cirq-google/cirq_google/api/v2/run_context_pb2.py
+++ b/cirq-google/cirq_google/api/v2/run_context_pb2.py
@@ -13,7 +13,7 @@
 
 
 
-DESCRIPTOR = _descriptor_pool.Default().AddSerializedFile(b'\n$cirq_google/api/v2/run_context.proto\x12\x12\x63irq.google.api.v2\"J\n\nRunContext\x12<\n\x10parameter_sweeps\x18\x01 \x03(\x0b\x32\".cirq.google.api.v2.ParameterSweep\"O\n\x0eParameterSweep\x12\x13\n\x0brepetitions\x18\x01 \x01(\x05\x12(\n\x05sweep\x18\x02 \x01(\x0b\x32\x19.cirq.google.api.v2.Sweep\"\x86\x01\n\x05Sweep\x12;\n\x0esweep_function\x18\x01 \x01(\x0b\x32!.cirq.google.api.v2.SweepFunctionH\x00\x12\x37\n\x0csingle_sweep\x18\x02 \x01(\x0b\x32\x1f.cirq.google.api.v2.SingleSweepH\x00\x42\x07\n\x05sweep\"\xc6\x01\n\rSweepFunction\x12\x45\n\rfunction_type\x18\x01 \x01(\x0e\x32..cirq.google.api.v2.SweepFunction.FunctionType\x12)\n\x06sweeps\x18\x02 \x03(\x0b\x32\x19.cirq.google.api.v2.Sweep\"C\n\x0c\x46unctionType\x12\x1d\n\x19\x46UNCTION_TYPE_UNSPECIFIED\x10\x00\x12\x0b\n\x07PRODUCT\x10\x01\x12\x07\n\x03ZIP\x10\x02\";\n\x0f\x44\x65viceParameter\x12\x0c\n\x04path\x18\x01 \x03(\t\x12\x0b\n\x03idx\x18\x02 \x01(\x03\x12\r\n\x05units\x18\x03 \x01(\t\"\xc5\x01\n\x0bSingleSweep\x12\x15\n\rparameter_key\x18\x01 \x01(\t\x12,\n\x06points\x18\x02 \x01(\x0b\x32\x1a.cirq.google.api.v2.PointsH\x00\x12\x30\n\x08linspace\x18\x03 \x01(\x0b\x32\x1c.cirq.google.api.v2.LinspaceH\x00\x12\x36\n\tparameter\x18\x04 \x01(\x0b\x32#.cirq.google.api.v2.DeviceParameterB\x07\n\x05sweep\"\x18\n\x06Points\x12\x0e\n\x06points\x18\x01 \x03(\x02\"G\n\x08Linspace\x12\x13\n\x0b\x66irst_point\x18\x01 \x01(\x02\x12\x12\n\nlast_point\x18\x02 \x01(\x02\x12\x12\n\nnum_points\x18\x03 \x01(\x03\x42\x32\n\x1d\x63om.google.cirq.google.api.v2B\x0fRunContextProtoP\x01\x62\x06proto3')
+DESCRIPTOR = _descriptor_pool.Default().AddSerializedFile(b'\n$cirq_google/api/v2/run_context.proto\x12\x12\x63irq.google.api.v2\"J\n\nRunContext\x12<\n\x10parameter_sweeps\x18\x01 \x03(\x0b\x32\".cirq.google.api.v2.ParameterSweep\"O\n\x0eParameterSweep\x12\x13\n\x0brepetitions\x18\x01 \x01(\x05\x12(\n\x05sweep\x18\x02 \x01(\x0b\x32\x19.cirq.google.api.v2.Sweep\"\x86\x01\n\x05Sweep\x12;\n\x0esweep_function\x18\x01 \x01(\x0b\x32!.cirq.google.api.v2.SweepFunctionH\x00\x12\x37\n\x0csingle_sweep\x18\x02 \x01(\x0b\x32\x1f.cirq.google.api.v2.SingleSweepH\x00\x42\x07\n\x05sweep\"\xc6\x01\n\rSweepFunction\x12\x45\n\rfunction_type\x18\x01 \x01(\x0e\x32..cirq.google.api.v2.SweepFunction.FunctionType\x12)\n\x06sweeps\x18\x02 \x03(\x0b\x32\x19.cirq.google.api.v2.Sweep\"C\n\x0c\x46unctionType\x12\x1d\n\x19\x46UNCTION_TYPE_UNSPECIFIED\x10\x00\x12\x0b\n\x07PRODUCT\x10\x01\x12\x07\n\x03ZIP\x10\x02\"W\n\x0f\x44\x65viceParameter\x12\x0c\n\x04path\x18\x01 \x03(\t\x12\x10\n\x03idx\x18\x02 \x01(\x03H\x00\x88\x01\x01\x12\x12\n\x05units\x18\x03 \x01(\tH\x01\x88\x01\x01\x42\x06\n\x04_idxB\x08\n\x06_units\"\xc5\x01\n\x0bSingleSweep\x12\x15\n\rparameter_key\x18\x01 \x01(\t\x12,\n\x06points\x18\x02 \x01(\x0b\x32\x1a.cirq.google.api.v2.PointsH\x00\x12\x30\n\x08linspace\x18\x03 \x01(\x0b\x32\x1c.cirq.google.api.v2.LinspaceH\x00\x12\x36\n\tparameter\x18\x04 \x01(\x0b\x32#.cirq.google.api.v2.DeviceParameterB\x07\n\x05sweep\"\x18\n\x06Points\x12\x0e\n\x06points\x18\x01 \x03(\x02\"G\n\x08Linspace\x12\x13\n\x0b\x66irst_point\x18\x01 \x01(\x02\x12\x12\n\nlast_point\x18\x02 \x01(\x02\x12\x12\n\nnum_points\x18\x03 \x01(\x03\x42\x32\n\x1d\x63om.google.cirq.google.api.v2B\x0fRunContextProtoP\x01\x62\x06proto3')
 
 _globals = globals()
 _builder.BuildMessageAndEnumDescriptors(DESCRIPTOR, _globals)
@@ -33,11 +33,11 @@
   _globals['_SWEEPFUNCTION_FUNCTIONTYPE']._serialized_start=486
   _globals['_SWEEPFUNCTION_FUNCTIONTYPE']._serialized_end=553
   _globals['_DEVICEPARAMETER']._serialized_start=555
-  _globals['_DEVICEPARAMETER']._serialized_end=614
-  _globals['_SINGLESWEEP']._serialized_start=617
-  _globals['_SINGLESWEEP']._serialized_end=814
-  _globals['_POINTS']._serialized_start=816
-  _globals['_POINTS']._serialized_end=840
-  _globals['_LINSPACE']._serialized_start=842
-  _globals['_LINSPACE']._serialized_end=913
+  _globals['_DEVICEPARAMETER']._serialized_end=642
+  _globals['_SINGLESWEEP']._serialized_start=645
+  _globals['_SINGLESWEEP']._serialized_end=842
+  _globals['_POINTS']._serialized_start=844
+  _globals['_POINTS']._serialized_end=868
+  _globals['_LINSPACE']._serialized_start=870
+  _globals['_LINSPACE']._serialized_end=941
 # @@protoc_insertion_point(module_scope)
diff --git a/cirq-google/cirq_google/api/v2/run_context_pb2.pyi b/cirq-google/cirq_google/api/v2/run_context_pb2.pyi
index 2c104967440..75afaa133e1 100644
--- a/cirq-google/cirq_google/api/v2/run_context_pb2.pyi
+++ b/cirq-google/cirq_google/api/v2/run_context_pb2.pyi
@@ -214,10 +214,15 @@ class DeviceParameter(google.protobuf.message.Message):
         self,
         *,
         path: collections.abc.Iterable[builtins.str] | None = ...,
-        idx: builtins.int = ...,
-        units: builtins.str = ...,
+        idx: builtins.int | None = ...,
+        units: builtins.str | None = ...,
     ) -> None: ...
-    def ClearField(self, field_name: typing_extensions.Literal["idx", b"idx", "path", b"path", "units", b"units"]) -> None: ...
+    def HasField(self, field_name: typing_extensions.Literal["_idx", b"_idx", "_units", b"_units", "idx", b"idx", "units", b"units"]) -> builtins.bool: ...
+    def ClearField(self, field_name: typing_extensions.Literal["_idx", b"_idx", "_units", b"_units", "idx", b"idx", "path", b"path", "units", b"units"]) -> None: ...
+    @typing.overload
+    def WhichOneof(self, oneof_group: typing_extensions.Literal["_idx", b"_idx"]) -> typing_extensions.Literal["idx"] | None: ...
+    @typing.overload
+    def WhichOneof(self, oneof_group: typing_extensions.Literal["_units", b"_units"]) -> typing_extensions.Literal["units"] | None: ...
 
 global___DeviceParameter = DeviceParameter
 
diff --git a/cirq-google/cirq_google/api/v2/sweeps.py b/cirq-google/cirq_google/api/v2/sweeps.py
index 0eb33e63bcf..6a6e1738424 100644
--- a/cirq-google/cirq_google/api/v2/sweeps.py
+++ b/cirq-google/cirq_google/api/v2/sweeps.py
@@ -105,7 +105,13 @@ def sweep_from_proto(msg: run_context_pb2.Sweep) -> cirq.Sweep:
         key = msg.single_sweep.parameter_key
         if msg.single_sweep.HasField("parameter"):
             metadata = DeviceParameter(
-                path=msg.single_sweep.parameter.path, idx=msg.single_sweep.parameter.idx
+                path=msg.single_sweep.parameter.path,
+                idx=msg.single_sweep.parameter.idx
+                if msg.single_sweep.parameter.HasField("idx")
+                else None,
+                units=msg.single_sweep.parameter.units
+                if msg.single_sweep.parameter.HasField("units")
+                else None,
             )
         else:
             metadata = None
diff --git a/cirq-google/cirq_google/api/v2/sweeps_test.py b/cirq-google/cirq_google/api/v2/sweeps_test.py
index f4cc144b40b..30a44573d39 100644
--- a/cirq-google/cirq_google/api/v2/sweeps_test.py
+++ b/cirq-google/cirq_google/api/v2/sweeps_test.py
@@ -52,6 +52,11 @@ def _values(self) -> Iterator[float]:
             [1, 1.5, 2, 2.5, 3],
             metadata=DeviceParameter(path=['path', 'to', 'parameter'], idx=2, units='GHz'),
         ),
+        cirq.Points(
+            'b',
+            [1, 1.5, 2, 2.5, 3],
+            metadata=DeviceParameter(path=['path', 'to', 'parameter'], idx=None),
+        ),
         cirq.Linspace('a', 0, 1, 5) * cirq.Linspace('b', 0, 1, 5),
         cirq.Points('a', [1, 2, 3]) + cirq.Linspace('b', 0, 1, 3),
         (
@@ -69,6 +74,8 @@ def test_sweep_to_proto_roundtrip(sweep):
     msg = v2.sweep_to_proto(sweep)
     deserialized = v2.sweep_from_proto(msg)
     assert deserialized == sweep
+    # Check that metadata is the same, if it exists.
+    assert getattr(deserialized, 'metadata', None) == getattr(sweep, 'metadata', None)
 
 
 def test_sweep_to_proto_linspace():