diff --git a/web/redux/redux-setup.js b/web/redux/redux-setup.js
--- a/web/redux/redux-setup.js
+++ b/web/redux/redux-setup.js
@@ -305,7 +305,7 @@
         ...state.threadStore,
         threadInfos: {
           ...state.threadStore.threadInfos,
-          [activeThread]: {
+          [(activeThread: string)]: {
             ...state.threadStore.threadInfos[activeThread],
             currentUser: {
               ...state.threadStore.threadInfos[activeThread].currentUser,
@@ -328,7 +328,7 @@
       ...state,
       threadActivityStore: {
         ...state.threadActivityStore,
-        [activeThread]: {
+        [(activeThread: string)]: {
           ...state.threadActivityStore[activeThread],
           lastNavigatedTo: now,
         },