diff --git a/src/matrix/storage/idb/Storage.js b/src/matrix/storage/idb/Storage.ts
similarity index 83%
rename from src/matrix/storage/idb/Storage.js
rename to src/matrix/storage/idb/Storage.ts
index d04183b6..747a9e16 100644
--- a/src/matrix/storage/idb/Storage.js
+++ b/src/matrix/storage/idb/Storage.ts
@@ -21,21 +21,26 @@ import { reqAsPromise } from "./utils";
 const WEBKITEARLYCLOSETXNBUG_BOGUS_KEY = "782rh281re38-boguskey";
 
 export class Storage {
-    constructor(idbDatabase, IDBKeyRange, hasWebkitEarlyCloseTxnBug) {
+    private _db: IDBDatabase;
+    private _hasWebkitEarlyCloseTxnBug: boolean;
+    storeNames: typeof StoreNames;
+
+    constructor(idbDatabase: IDBDatabase, IDBKeyRange, hasWebkitEarlyCloseTxnBug: boolean) {
         this._db = idbDatabase;
+        // @ts-ignore
         this._IDBKeyRange = IDBKeyRange;
         this._hasWebkitEarlyCloseTxnBug = hasWebkitEarlyCloseTxnBug;
         this.storeNames = StoreNames;
     }
 
-    _validateStoreNames(storeNames) {
+    _validateStoreNames(storeNames: StoreNames[]): void {
         const idx = storeNames.findIndex(name => !STORE_NAMES.includes(name));
         if (idx !== -1) {
             throw new StorageError(`Tried top, a transaction unknown store ${storeNames[idx]}`);
         }
     }
 
-    async readTxn(storeNames) {
+    async readTxn(storeNames: StoreNames[]): Promise<Transaction> {
         this._validateStoreNames(storeNames);
         try {
             const txn = this._db.transaction(storeNames, "readonly");
@@ -44,13 +49,14 @@ export class Storage {
             if (this._hasWebkitEarlyCloseTxnBug) {
                 await reqAsPromise(txn.objectStore(storeNames[0]).get(WEBKITEARLYCLOSETXNBUG_BOGUS_KEY));
             }
+            // @ts-ignore
             return new Transaction(txn, storeNames, this._IDBKeyRange);
         } catch(err) {
             throw new StorageError("readTxn failed", err);
         }
     }
 
-    async readWriteTxn(storeNames) {
+    async readWriteTxn(storeNames: StoreNames[]): Promise<Transaction> {
         this._validateStoreNames(storeNames);
         try {
             const txn = this._db.transaction(storeNames, "readwrite");
@@ -59,13 +65,14 @@ export class Storage {
             if (this._hasWebkitEarlyCloseTxnBug) {
                 await reqAsPromise(txn.objectStore(storeNames[0]).get(WEBKITEARLYCLOSETXNBUG_BOGUS_KEY));
             }
+            // @ts-ignore
             return new Transaction(txn, storeNames, this._IDBKeyRange);
         } catch(err) {
             throw new StorageError("readWriteTxn failed", err);
         }
     }
 
-    close() {
+    close(): void {
         this._db.close();
     }
 }
diff --git a/src/matrix/storage/idb/StorageFactory.js b/src/matrix/storage/idb/StorageFactory.js
index a9dc8eed..84b699eb 100644
--- a/src/matrix/storage/idb/StorageFactory.js
+++ b/src/matrix/storage/idb/StorageFactory.js
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {Storage} from "./Storage.js";
+import {Storage} from "./Storage";
 import { openDatabase, reqAsPromise } from "./utils";
 import { exportSession, importSession } from "./export.js";
 import { schema } from "./schema.js";