diff --git a/src/store.js b/src/store.js
index c4f7a84..801d089 100644
--- a/src/store.js
+++ b/src/store.js
@@ -9,6 +9,9 @@ export const timetableClass = ref(
 );
 
 watch(substitutionFilter, (newValue) => {
+  if (newValue == "other") {
+    newValue = prompt("Please enter a class to filter (e.g. 9C)");
+  }
   localStorage.setItem("substitutionFilter", newValue);
 });
 watch(timetableClass, (newValue) => {