diff --git a/pkgs/by-name/ni/nixos-rebuild-ng/src/nixos_rebuild/__init__.py b/pkgs/by-name/ni/nixos-rebuild-ng/src/nixos_rebuild/__init__.py
index 8ce9c9b2d7f0..11ebd6dfdfa0 100644
--- a/pkgs/by-name/ni/nixos-rebuild-ng/src/nixos_rebuild/__init__.py
+++ b/pkgs/by-name/ni/nixos-rebuild-ng/src/nixos_rebuild/__init__.py
@@ -56,7 +56,13 @@ def get_parser() -> tuple[argparse.ArgumentParser, dict[str, argparse.ArgumentPa
 
     copy_flags = argparse.ArgumentParser(add_help=False)
     copy_flags.add_argument(
-        "--use-substitutes", "--substitute-on-destination", "-s", action="store_true"
+        "--use-substitutes",
+        "--substitute-on-destination",
+        "-s",
+        action="store_true",
+        # `-s` is the destination since it has the same meaning in
+        # `nix-copy-closure` and `nix copy`
+        dest="s",
     )
 
     sub_parsers = {
diff --git a/pkgs/by-name/ni/nixos-rebuild-ng/src/nixos_rebuild/utils.py b/pkgs/by-name/ni/nixos-rebuild-ng/src/nixos_rebuild/utils.py
index cd89435f2d4f..b1d94114fa51 100644
--- a/pkgs/by-name/ni/nixos-rebuild-ng/src/nixos_rebuild/utils.py
+++ b/pkgs/by-name/ni/nixos-rebuild-ng/src/nixos_rebuild/utils.py
@@ -1,5 +1,5 @@
 import logging
-from typing import TypeAlias, override
+from typing import TypeAlias, assert_never, override
 
 Args: TypeAlias = bool | str | list[str] | int | None
 
@@ -25,6 +25,8 @@ def dict_to_flags(d: dict[str, Args]) -> list[str]:
         match value:
             case None | False | 0 | []:
                 continue
+            case True if len(key) == 1:
+                flags.append(f"-{key}")
             case True:
                 flags.append(flag)
             case int():
@@ -36,4 +38,6 @@ def dict_to_flags(d: dict[str, Args]) -> list[str]:
                 flags.append(flag)
                 for v in value:
                     flags.append(v)
+            case _:
+                assert_never(value)
     return flags
diff --git a/pkgs/by-name/ni/nixos-rebuild-ng/src/tests/test_utils.py b/pkgs/by-name/ni/nixos-rebuild-ng/src/tests/test_utils.py
index 0e5eb7437f65..36b8024a4e56 100644
--- a/pkgs/by-name/ni/nixos-rebuild-ng/src/tests/test_utils.py
+++ b/pkgs/by-name/ni/nixos-rebuild-ng/src/tests/test_utils.py
@@ -9,6 +9,7 @@ def test_dict_to_flags() -> None:
             "test_flag_3": "value",
             "test_flag_4": ["v1", "v2"],
             "test_flag_5": None,
+            "t": True,
             "verbose": 5,
         }
     )
@@ -19,6 +20,7 @@ def test_dict_to_flags() -> None:
         "--test-flag-4",
         "v1",
         "v2",
+        "-t",
         "-vvvvv",
     ]
     r2 = u.dict_to_flags({"verbose": 0, "empty_list": []})