diff --git a/lib/reducers/alert-reducer.js b/lib/reducers/alert-reducer.js
--- a/lib/reducers/alert-reducer.js
+++ b/lib/reducers/alert-reducer.js
@@ -39,7 +39,7 @@
       ...state,
       alertInfos: {
         ...state.alertInfos,
-        [(action.payload.alertType: string)]: {
+        [action.payload.alertType]: {
           ...state.alertInfos[action.payload.alertType],
           totalAlerts:
             state.alertInfos[action.payload.alertType].totalAlerts + 1,