diff --git a/src/restic/docker.py b/src/restic/docker.py
index ee58a85..a673dac 100644
--- a/src/restic/docker.py
+++ b/src/restic/docker.py
@@ -18,7 +18,7 @@ def manage_containers(project: str, services: list[str]):
                     for c in client.containers.list()
                     if c.labels['com.docker.compose.project'] == project
                 )
-                service_dict = {
+                service_dict: dict[str, Container] = {
                     c.labels['com.docker.compose.service']: c for c in project_containers
                 }
                 containers: list[Container] = [service_dict[s] for s in services]