diff --git a/pool.js b/pool.js
index 867e61b..4d6a42a 100644
--- a/pool.js
+++ b/pool.js
@@ -72,17 +72,18 @@ function compute_filtration_time(t) {
 // [ start1, stop1, start2, stop2, ... ]
 
 function compute_schedule_filt(d) {
-  let start = 17 - d/2;
-  let stop = 17 + d/2;
+  let t_start = 17 - d/2;
+  let t_stop = 17 + d/2;
 
-  while (stop >= 24)
-    stop = stop - 24;
+  while (t_stop >= 24)
+    t_stop = t_stop - 24;
 
+  let s;
   if (d < 24) {
-    let s = [ start, stop ];
+    s = [ t_start, t_stop ];
   }
   else {
-    let s = [ start ];
+    s = [ t_start ];
   }
 
   return s;