diff --git a/nixops/__main__.py b/nixops/__main__.py
index 67fce0eac..b845587ba 100755
--- a/nixops/__main__.py
+++ b/nixops/__main__.py
@@ -2,7 +2,7 @@
 # -*- coding: utf-8 -*-
 
 from nixops import deployment
-from argparse import ArgumentParser, SUPPRESS, REMAINDER
+from argparse import ArgumentParser, _SubParsersAction, SUPPRESS, REMAINDER
 import os
 from nixops.script_defs import *
 
@@ -10,7 +10,7 @@
 parser = ArgumentParser(description="NixOS cloud deployment tool", prog="nixops")
 parser.add_argument("--version", action="version", version="NixOps @version@")
 
-subparsers = parser.add_subparsers(
+subparsers: _SubParsersAction = parser.add_subparsers(
     help="sub-command help", metavar="operation", required=True
 )
 
diff --git a/nixops/script_defs.py b/nixops/script_defs.py
index 48fdbc78b..9a263b40e 100644
--- a/nixops/script_defs.py
+++ b/nixops/script_defs.py
@@ -7,7 +7,7 @@
 
 import nixops.statefile
 import prettytable
-from argparse import Namespace
+from argparse import ArgumentParser, _SubParsersAction, Namespace
 import os
 import pwd
 import re
@@ -974,7 +974,9 @@ def setup_logging(args):
         nixops.util.TeeStdout()
 
 
-def add_subparser(subparsers, name, help):
+def add_subparser(
+    subparsers: _SubParsersAction, name: str, help: str
+) -> ArgumentParser:
     subparser = subparsers.add_parser(name, help=help)
     subparser.add_argument(
         "--state",
@@ -1062,7 +1064,7 @@ def add_subparser(subparsers, name, help):
     return subparser
 
 
-def add_common_modify_options(subparser):
+def add_common_modify_options(subparser: ArgumentParser):
     subparser.add_argument(
         "nix_exprs",
         nargs="*",
@@ -1079,7 +1081,7 @@ def add_common_modify_options(subparser):
     )
 
 
-def add_common_deployment_options(subparser):
+def add_common_deployment_options(subparser: ArgumentParser):
     subparser.add_argument(
         "--include",
         nargs="+",