diff --git a/src/components/cylc/tree/Tree.vue b/src/components/cylc/tree/Tree.vue
index dedc28157..ceb3250bc 100644
--- a/src/components/cylc/tree/Tree.vue
+++ b/src/components/cylc/tree/Tree.vue
@@ -218,6 +218,9 @@ export default {
       })
     },
     tasksFilterStates: function () {
+      if (!this.activeFilters) {
+        return []
+      }
       return this.activeFilters.states.map(selectedTaskState => {
         return selectedTaskState
       })