diff --git a/nixosModules/clanCore/networking.nix b/nixosModules/clanCore/networking.nix
index 048e52da..f6f8d93a 100644
--- a/nixosModules/clanCore/networking.nix
+++ b/nixosModules/clanCore/networking.nix
@@ -14,7 +14,8 @@
           - user@machine2.example.com
           - root@example.com:2222&IdentityFile=/path/to/private/key
       '';
-      type = lib.types.str;
+      default = null;
+      type = lib.types.nullOr lib.types.str;
     };
     buildHost = lib.mkOption {
       description = ''
diff --git a/nixosModules/clanCore/outputs.nix b/nixosModules/clanCore/outputs.nix
index d5f39bf9..924728cb 100644
--- a/nixosModules/clanCore/outputs.nix
+++ b/nixosModules/clanCore/outputs.nix
@@ -20,13 +20,13 @@
           '';
         };
         deployment.buildHost = lib.mkOption {
-          type = lib.types.str;
+          type = lib.types.nullOr lib.types.str;
           description = ''
             the hostname of the build host where nixos-rebuild is run
           '';
         };
         deployment.targetHost = lib.mkOption {
-          type = lib.types.str;
+          type = lib.types.nullOr lib.types.str;
           description = ''
             the hostname of the target host to be deployed to
           '';
diff --git a/pkgs/clan-cli/clan_cli/machines/machines.py b/pkgs/clan-cli/clan_cli/machines/machines.py
index 2ed45746..b1c7eeee 100644
--- a/pkgs/clan-cli/clan_cli/machines/machines.py
+++ b/pkgs/clan-cli/clan_cli/machines/machines.py
@@ -3,6 +3,7 @@ import logging
 from pathlib import Path
 
 from ..cmd import run
+from ..errors import ClanError
 from ..nix import nix_build, nix_config, nix_eval, nix_metadata
 from ..ssh import Host, parse_deployment_address
 
@@ -48,10 +49,14 @@ class Machine:
     @property
     def target_host(self) -> str:
         # deploymentAddress is deprecated.
-        return (
+        val = (
             self.deployment_info.get("targetHost")
             or self.deployment_info["deploymentAddress"]
         )
+        if val is None:
+            msg = f"the 'clan.networking.targetHost' nixos option is not set for machine '{self.name}'"
+            raise ClanError(msg)
+        return val
 
     @target_host.setter
     def target_host(self, value: str) -> None:
diff --git a/pkgs/clan-cli/clan_cli/machines/update.py b/pkgs/clan-cli/clan_cli/machines/update.py
index dbb2114c..d613c106 100644
--- a/pkgs/clan-cli/clan_cli/machines/update.py
+++ b/pkgs/clan-cli/clan_cli/machines/update.py
@@ -154,14 +154,11 @@ def get_all_machines(clan_dir: Path) -> HostGroup:
     hosts = []
     for name, machine_data in machines.items():
         # very hacky. would be better to do a MachinesGroup instead
+        machine = Machine(name=name, flake=clan_dir, deployment_info=machine_data)
         host = parse_deployment_address(
             name,
-            machine_data.get("targetHost") or machine_data.get("deploymentAddress"),
-            meta={
-                "machine": Machine(
-                    name=name, flake=clan_dir, deployment_info=machine_data
-                )
-            },
+            host=machine.target_host,
+            meta={"machine": machine},
         )
         hosts.append(host)
     return HostGroup(hosts)