diff --git a/nix/modules/hive-forge.nix b/nix/modules/hive-forge.nix
index b35ea33..885acec 100644
--- a/nix/modules/hive-forge.nix
+++ b/nix/modules/hive-forge.nix
@@ -112,6 +112,11 @@ in
                 DEFAULT_PRIVATE = "private";
               };
               log.LEVEL = "Warn";
+              # F3 (federation) computes its data dir relative to the
+              # forgejo binary, which lands in the read-only nix
+              # store and crashes the daemon at boot. We don't
+              # federate; turn it off.
+              "F3".ENABLED = false;
             };
           };
           environment.systemPackages = [ pkgs.forgejo ];