diff --git a/pkgs/clan-cli/clan_cli/completions.py b/pkgs/clan-cli/clan_cli/completions.py
index aad1b9ebf..63d588d88 100644
--- a/pkgs/clan-cli/clan_cli/completions.py
+++ b/pkgs/clan-cli/clan_cli/completions.py
@@ -478,6 +478,17 @@ def complete_tags(
     return dict.fromkeys(tags, "tag")
 
 
+def complete_build_host(
+    prefix: str,  # noqa: ARG001
+    _parsed_args: argparse.Namespace,
+    **_kwargs: Any,
+) -> Iterable[str]:
+    """Provides completion functionality for build host.
+    Returns 'localhost' as a suggestion while allowing arbitrary SSH addresses.
+    """
+    return dict.fromkeys(["localhost"], "build_host")
+
+
 def add_dynamic_completer(
     action: argparse.Action,
     completer: Callable[..., Iterable[str]],
diff --git a/pkgs/clan-cli/clan_cli/machines/update.py b/pkgs/clan-cli/clan_cli/machines/update.py
index 57a4cb889..1918fc4b1 100644
--- a/pkgs/clan-cli/clan_cli/machines/update.py
+++ b/pkgs/clan-cli/clan_cli/machines/update.py
@@ -20,6 +20,7 @@ from clan_lib.ssh.remote import Remote
 
 from clan_cli.completions import (
     add_dynamic_completer,
+    complete_build_host,
     complete_machines,
     complete_tags,
 )
@@ -238,7 +239,7 @@ def register_update_parser(parser: argparse.ArgumentParser) -> None:
         type=str,
         help="Address of the machine to update, in the format of user@host:1234.",
     )
-    parser.add_argument(
+    build_host_parser = parser.add_argument(
         "--build-host",
         type=str,
         help=(
@@ -246,6 +247,7 @@ def register_update_parser(parser: argparse.ArgumentParser) -> None:
             "Pass 'localhost' to build on the local machine, or an ssh address like user@host:1234\n"
         ),
     )
+    add_dynamic_completer(build_host_parser, complete_build_host)
     parser.add_argument(
         "--upload-inputs",
         action="store_true",