diff --git a/python/BUILD.bazel b/python/BUILD.bazel
index a05fb6ec7..48d7d3f58 100644
--- a/python/BUILD.bazel
+++ b/python/BUILD.bazel
@@ -34,3 +34,39 @@ py_test(
         "@abseil-py//absl/testing:parameterized",
     ],
 )
+
+# These are implementation details for `setup.py`, so they can be
+# named however we want. For now, they are named to be consistent
+# with the `--cpu` flag values that they will eventually replace.
+
+platform(
+    name = "darwin_x86_64",
+    constraint_values = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:macos",
+    ],
+)
+
+platform(
+    name = "darwin_arm64",
+    constraint_values = [
+        "@platforms//cpu:arm64",
+        "@platforms//os:macos",
+    ],
+)
+
+platform(
+    name = "x64_x86_windows",
+    constraint_values = [
+        "@platforms//cpu:x86_32",
+        "@platforms//os:windows",
+    ],
+)
+
+platform(
+    name = "x64_windows",
+    constraint_values = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:windows",
+    ],
+)
diff --git a/python/setup.py b/python/setup.py
index 3bd11edb7..7d83b3447 100644
--- a/python/setup.py
+++ b/python/setup.py
@@ -54,6 +54,7 @@ def build_extension(self, ext):
     cmd = ['bazel', 'build']
     try:
       cmd.append(f'--cpu={os.environ["BAZEL_CPU"].lower()}')
+      cmd.append(f'--platforms=//python:{os.environ["BAZEL_CPU"].lower()}')
     except KeyError:
       pass
     cmd += ['--compilation_mode=opt', '--', ':all']