diff --git a/src/matrix/storage/idb/Store.ts b/src/matrix/storage/idb/Store.ts
index 890785bd..9c49dc57 100644
--- a/src/matrix/storage/idb/Store.ts
+++ b/src/matrix/storage/idb/Store.ts
@@ -35,7 +35,7 @@ class QueryTargetWrapper<T> {
     }
 
     get keyPath(): string | string[] {
-        if (this._qt["objectStore"]) {
+        if ("objectStore" in this._qt) {
             return (this._qt as IDBIndex).objectStore.keyPath;
         } else {
             return this._qt.keyPath;