diff --git a/buildbot_nix/__init__.py b/buildbot_nix/__init__.py
index 3d706f6..4dc338a 100644
--- a/buildbot_nix/__init__.py
+++ b/buildbot_nix/__init__.py
@@ -734,7 +734,7 @@ class NixConfigurator(ConfiguratorBase):
         for item in worker_config:
             cores = item.get("cores", 0)
             for i in range(cores):
-                worker_name = f"{item['name']}-{i}"
+                worker_name = f"{item['name']}-{i:03}"
                 config["workers"].append(worker.Worker(worker_name, item["pass"]))
                 worker_names.append(worker_name)
 
diff --git a/buildbot_nix/worker.py b/buildbot_nix/worker.py
index 7e1181e..65d0f8b 100644
--- a/buildbot_nix/worker.py
+++ b/buildbot_nix/worker.py
@@ -29,11 +29,11 @@ class WorkerConfig:
 def setup_worker(
     application: service.Application, id: int, config: WorkerConfig
 ) -> None:
-    basedir = f"{config.buildbot_dir}-{id}"
+    basedir = f"{config.buildbot_dir}-{id:03}"
     os.makedirs(basedir, mode=0o700, exist_ok=True)
 
     hostname = socket.gethostname()
-    workername = f"{hostname}-{id}"
+    workername = f"{hostname}-{id:03}"
     keepalive = 600
     umask = None
     maxdelay = 300