diff --git a/nix/modules/hive-ci.nix b/nix/modules/hive-ci.nix
index 188b960c..a5be370f 100644
--- a/nix/modules/hive-ci.nix
+++ b/nix/modules/hive-ci.nix
@@ -282,8 +282,12 @@ in
           # execution environment. The gitea-actions-runner host scheme
           # spawns job processes with the service's environment; without
           # this PATH override, `nix` and `git` aren't visible to steps.
+          # mkForce is required: the nixpkgs gitea-actions-runner module
+          # also sets PATH in the service environment, so without an
+          # explicit priority the evaluator raises a conflicting
+          # definition error.
           systemd.services."gitea-runner-hive".environment.PATH =
-            "/run/current-system/sw/bin:/nix/var/nix/profiles/default/bin:/usr/bin:/bin";
+            lib.mkForce "/run/current-system/sw/bin:/nix/var/nix/profiles/default/bin:/usr/bin:/bin";
         };
     };
   };