diff --git a/nextstrain/cli/runner/__init__.py b/nextstrain/cli/runner/__init__.py
index f9fffcc2..0aaefd0e 100644
--- a/nextstrain/cli/runner/__init__.py
+++ b/nextstrain/cli/runner/__init__.py
@@ -1,7 +1,8 @@
 import argparse
-import builtins
 from argparse import ArgumentParser
 from typing import cast, List, Union, TYPE_CHECKING
+# TODO: Use typing.TypeAlias once Python 3.10 is the minimum supported version.
+from typing_extensions import TypeAlias
 from . import (
     docker as __docker,
     conda as __conda,
@@ -12,7 +13,7 @@
 from .. import config, env, hostenv
 from ..argparse import DirectoryPath, SKIP_AUTO_DEFAULT_IN_HELP
 from ..errors import UserError
-from ..types import Env, Options, RunnerModule
+from ..types import EllipsisType, Env, Options, RunnerModule
 from ..util import prose_list, runner_name, runner_module, runner_help, warn
 from ..volume import NamedVolume
 
@@ -70,7 +71,7 @@
             % (configured_runner, runner_name(default_runner)))
 
 
-RunnerExec = List[Union[str, 'builtins.ellipsis']]
+RunnerExec: TypeAlias = List[Union[str, EllipsisType]]
 
 
 def register_runners(parser:  ArgumentParser,
diff --git a/nextstrain/cli/types.py b/nextstrain/cli/types.py
index c4982675..a6df8229 100644
--- a/nextstrain/cli/types.py
+++ b/nextstrain/cli/types.py
@@ -4,13 +4,21 @@
 
 import argparse
 import builtins
+import sys
 import urllib.parse
 from pathlib import Path
 from typing import Any, Iterable, List, Mapping, Optional, Tuple, Union
 # TODO: Use typing.Protocol once Python 3.8 is the minimum supported version.
-from typing_extensions import Protocol
+# TODO: Use typing.TypeAlias once Python 3.10 is the minimum supported version.
+from typing_extensions import Protocol, TypeAlias
 from .volume import NamedVolume
 
+# Re-export EllipsisType so we can paper over its absence from older Pythons
+if sys.version_info >= (3, 10):
+    from types import EllipsisType
+else:
+    EllipsisType: TypeAlias = 'builtins.ellipsis'
+
 """
 An immutable mapping of (*name*, *value*) pairs representing a set of
 additional environment variables to overlay on the current environment (e.g.
@@ -32,7 +40,7 @@
 
 RunnerTestResults = List['RunnerTestResult']
 RunnerTestResult  = Tuple[str, 'RunnerTestResultStatus']
-RunnerTestResultStatus = Union[bool, None, 'builtins.ellipsis']
+RunnerTestResultStatus: TypeAlias = Union[bool, None, EllipsisType]
 
 RunnerUpdateStatus = Optional[bool]