diff --git a/krebs/3modules/buildbot/master.nix b/krebs/3modules/buildbot/master.nix
index 8995753ac..a845bb281 100644
--- a/krebs/3modules/buildbot/master.nix
+++ b/krebs/3modules/buildbot/master.nix
@@ -322,6 +322,7 @@ let
       description = "Buildbot Master";
       home = cfg.workDir;
       createHome = false;
+      isSystemUser = true;
     };
 
     users.extraGroups.buildbotMaster = {
diff --git a/krebs/3modules/buildbot/slave.nix b/krebs/3modules/buildbot/slave.nix
index c15169fba..d877b9911 100644
--- a/krebs/3modules/buildbot/slave.nix
+++ b/krebs/3modules/buildbot/slave.nix
@@ -131,6 +131,7 @@ let
       description = "Buildbot Slave";
       home = cfg.workDir;
       createHome = false;
+      isSystemUser = true;
     };
 
     users.extraGroups.buildbotSlave = {