diff --git a/pool.js b/pool.js
index 8e4e444..867e61b 100644
--- a/pool.js
+++ b/pool.js
@@ -183,7 +183,7 @@ function update_pump(temp, max, time) {
   }
 
   // compute the current switch state according to the schedule
-  let on = false;
+  on = false;
   if (schedule.length === 1) {
     on = true;
   }