--- a/proton/vpn/cli/commands/settings.py
+++ b/proton/vpn/cli/commands/settings.py
@@ -20,6 +20,7 @@
 """
 import click
 from tabulate import tabulate
+from typing import Optional
 
 from proton.vpn.cli._cli_constants import PROGRAM_NAME
 from proton.vpn.cli.core.run_async import run_async
@@ -244,7 +245,7 @@
 @click.option("--dns", "dns_csv", help="Comma-separated DNS server IPs (IPv4 or IPv6)")
 @click.pass_context
 @run_async
-async def custom_dns_command(ctx: click.Context, state: str, dns_csv: str | None) -> None:
+async def custom_dns_command(ctx: click.Context, state: str, dns_csv: Optional[str]) -> None:
     """Configure custom DNS servers."""
     controller = await Controller.create(params=ctx.obj, click_ctx=ctx)
     toggle_value = ToggleType.from_str(state)