diff --git a/cibuildwheel/oci_container.py b/cibuildwheel/oci_container.py
index ac71e9844..e07001268 100644
--- a/cibuildwheel/oci_container.py
+++ b/cibuildwheel/oci_container.py
@@ -32,7 +32,7 @@ class OCIContainerEngineConfig:
     def from_config_string(config_string: str) -> OCIContainerEngineConfig:
         config_dict = parse_key_value_string(config_string, ["name"])
         name = " ".join(config_dict["name"])
-        if name not in ["docker", "podman"]:
+        if name not in {"docker", "podman"}:
             msg = f"unknown container engine {name}"
             raise ValueError(msg)
 
diff --git a/unit_test/oci_container_test.py b/unit_test/oci_container_test.py
index 617529cad..ccbd05555 100644
--- a/unit_test/oci_container_test.py
+++ b/unit_test/oci_container_test.py
@@ -21,7 +21,7 @@
 pm = platform.machine()
 if pm == "x86_64":
     DEFAULT_IMAGE = "quay.io/pypa/manylinux2014_x86_64:2020-05-17-2f8ac3b"
-elif pm in ["aarch64", "arm64"]:
+elif pm in {"aarch64", "arm64"}:
     DEFAULT_IMAGE = "quay.io/pypa/manylinux2014_aarch64:2020-05-17-2f8ac3b"
 elif pm == "ppc64le":
     DEFAULT_IMAGE = "quay.io/pypa/manylinux2014_ppc64le:2020-05-17-2f8ac3b"