diff --git a/.circleci/config.yml b/.circleci/config.yml
index 6fa1106fc..50191555f 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -441,7 +441,7 @@ jobs:
         image: "tahoelafsci/fedora:29-py"
         user: "nobody"
 
-  nixos-21.05: &NIXOS
+  nixos-21-05: &NIXOS
     docker:
       # Run in a highly Nix-capable environment.
       - <<: *DOCKERHUB_AUTH