diff --git a/modal/sandbox.py b/modal/sandbox.py
index 197f3d172..fea25e987 100644
--- a/modal/sandbox.py
+++ b/modal/sandbox.py
@@ -27,6 +27,7 @@
 from .mount import _Mount
 from .network_file_system import _NetworkFileSystem, network_file_system_mount_protos
 from .object import _get_environment_name, _Object
+from .proxy import _Proxy
 from .scheduler_placement import SchedulerPlacement
 from .secret import _Secret
 from .stream_type import StreamType
@@ -72,6 +73,7 @@ def _new(
         pty_info: Optional[api_pb2.PTYInfo] = None,
         encrypted_ports: Sequence[int] = [],
         unencrypted_ports: Sequence[int] = [],
+        proxy: Optional[_Proxy] = None,
         _experimental_scheduler_placement: Optional[SchedulerPlacement] = None,
     ) -> "_Sandbox":
         """mdmd:hidden"""
@@ -165,6 +167,7 @@ async def _load(self: _Sandbox, resolver: Resolver, _existing_object_id: Optiona
                 worker_id=config.get("worker_id"),
                 open_ports=api_pb2.PortSpecs(ports=open_ports),
                 network_access=network_access,
+                proxy_id=(proxy.object_id if proxy else None),
             )
 
             # Note - `resolver.app_id` will be `None` for app-less sandboxes
diff --git a/modal_proto/api.proto b/modal_proto/api.proto
index 9f247233d..17de79a37 100644
--- a/modal_proto/api.proto
+++ b/modal_proto/api.proto
@@ -2082,6 +2082,8 @@ message Sandbox {
 
   // Network access configuration beyond simple allow/block.
   NetworkAccess network_access = 22;
+
+  optional string proxy_id = 23;
 }
 
 message SandboxCreateRequest {