diff --git a/build/siso/backend.star b/build/siso/backend.star
new file mode 100644
index 0000000000..72eb0555d3
--- /dev/null
+++ b/build/siso/backend.star
@@ -0,0 +1,21 @@
+# -*- bazel-starlark -*-
+
+load("@builtin//struct.star", "module")
+
+def __platform_properties(ctx):
+    container_image = "docker://gcr.io/chops-public-images-prod/rbe/siso-chromium/linux@sha256:ef35d347f4a4a2d32b76fd908e66e96f59bf8ba7379fd5626548244c45343b2b"
+    return {
+        "default": {
+            "OSFamily": "Linux",
+            "container-image": container_image,
+        },
+        "large": {
+            "OSFamily": "Linux",
+            "container-image": container_image,
+        },
+    }
+
+backend = module(
+    "backend",
+    platform_properties = __platform_properties,
+)