diff --git a/nixos/modules/services/monitoring/prometheus/default.nix b/nixos/modules/services/monitoring/prometheus/default.nix
index e08f23d8eb04..8fe689ef3dbb 100644
--- a/nixos/modules/services/monitoring/prometheus/default.nix
+++ b/nixos/modules/services/monitoring/prometheus/default.nix
@@ -945,6 +945,7 @@ in {
         RuntimeDirectoryMode = "0700";
         WorkingDirectory = workingDir;
         StateDirectory = cfg.stateDir;
+        StateDirectoryMode = "0700";
       };
     };
   };