diff --git a/nixos/modules/services/misc/fstrim.nix b/nixos/modules/services/misc/fstrim.nix
index 36b5f9c8cca1..55fb24e29272 100644
--- a/nixos/modules/services/misc/fstrim.nix
+++ b/nixos/modules/services/misc/fstrim.nix
@@ -34,7 +34,7 @@ in {
 
     systemd.timers.fstrim = {
       timerConfig = {
-        OnCalendar = cfg.interval;
+        OnCalendar = [ "" cfg.interval ];
       };
       wantedBy = [ "timers.target" ];
     };