diff --git a/src/matrix/storage/idb/QueryTarget.js b/src/matrix/storage/idb/QueryTarget.js
index 348e67f9..c2657c52 100644
--- a/src/matrix/storage/idb/QueryTarget.js
+++ b/src/matrix/storage/idb/QueryTarget.js
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {iterateCursor, reqAsPromise} from "./utils.js";
+import {iterateCursor, reqAsPromise} from "./utils";
 
 export class QueryTarget {
     constructor(target) {
diff --git a/src/matrix/storage/idb/Storage.js b/src/matrix/storage/idb/Storage.js
index 0a357dda..cef636fb 100644
--- a/src/matrix/storage/idb/Storage.js
+++ b/src/matrix/storage/idb/Storage.js
@@ -16,7 +16,7 @@ limitations under the License.
 
 import {Transaction} from "./Transaction.js";
 import { STORE_NAMES, StorageError } from "../common";
-import { reqAsPromise } from "./utils.js";
+import { reqAsPromise } from "./utils";
 
 const WEBKITEARLYCLOSETXNBUG_BOGUS_KEY = "782rh281re38-boguskey";
 
diff --git a/src/matrix/storage/idb/StorageFactory.js b/src/matrix/storage/idb/StorageFactory.js
index 719d2672..a9dc8eed 100644
--- a/src/matrix/storage/idb/StorageFactory.js
+++ b/src/matrix/storage/idb/StorageFactory.js
@@ -15,7 +15,7 @@ limitations under the License.
 */
 
 import {Storage} from "./Storage.js";
-import { openDatabase, reqAsPromise } from "./utils.js";
+import { openDatabase, reqAsPromise } from "./utils";
 import { exportSession, importSession } from "./export.js";
 import { schema } from "./schema.js";
 import { detectWebkitEarlyCloseTxnBug } from "./quirks.js";
diff --git a/src/matrix/storage/idb/Transaction.js b/src/matrix/storage/idb/Transaction.js
index ae0f75be..d1c91d69 100644
--- a/src/matrix/storage/idb/Transaction.js
+++ b/src/matrix/storage/idb/Transaction.js
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {txnAsPromise} from "./utils.js";
+import {txnAsPromise} from "./utils";
 import {StorageError} from "../common";
 import {Store} from "./Store.js";
 import {SessionStore} from "./stores/SessionStore.js";
diff --git a/src/matrix/storage/idb/export.js b/src/matrix/storage/idb/export.js
index 34dd8706..27979ce0 100644
--- a/src/matrix/storage/idb/export.js
+++ b/src/matrix/storage/idb/export.js
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { iterateCursor, txnAsPromise } from "./utils.js";
+import { iterateCursor, txnAsPromise } from "./utils";
 import { STORE_NAMES } from "../common";
 
 export async function exportSession(db) {
diff --git a/src/matrix/storage/idb/quirks.js b/src/matrix/storage/idb/quirks.js
index 9739b7da..5eaa6836 100644
--- a/src/matrix/storage/idb/quirks.js
+++ b/src/matrix/storage/idb/quirks.js
@@ -15,7 +15,7 @@ limitations under the License.
 */
 
 
-import {openDatabase, txnAsPromise, reqAsPromise} from "./utils.js";
+import {openDatabase, txnAsPromise, reqAsPromise} from "./utils";
 
 // filed as https://bugs.webkit.org/show_bug.cgi?id=222746
 export async function detectWebkitEarlyCloseTxnBug(idbFactory) {
diff --git a/src/matrix/storage/idb/schema.js b/src/matrix/storage/idb/schema.js
index 352c810c..d593f6b9 100644
--- a/src/matrix/storage/idb/schema.js
+++ b/src/matrix/storage/idb/schema.js
@@ -1,4 +1,4 @@
-import {iterateCursor, reqAsPromise} from "./utils.js";
+import {iterateCursor, reqAsPromise} from "./utils";
 import {RoomMember, EVENT_TYPE as MEMBER_EVENT_TYPE} from "../../room/members/RoomMember.js";
 import {RoomMemberStore} from "./stores/RoomMemberStore.js";
 import {SessionStore} from "./stores/SessionStore.js";
diff --git a/src/matrix/storage/idb/stores/PendingEventStore.js b/src/matrix/storage/idb/stores/PendingEventStore.js
index 385f3c9a..61071f11 100644
--- a/src/matrix/storage/idb/stores/PendingEventStore.js
+++ b/src/matrix/storage/idb/stores/PendingEventStore.js
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { encodeUint32, decodeUint32 } from "../utils.js";
+import { encodeUint32, decodeUint32 } from "../utils";
 import {KeyLimits} from "../../common";
 
 function encodeKey(roomId, queueIndex) {
diff --git a/src/matrix/storage/idb/stores/TimelineEventStore.js b/src/matrix/storage/idb/stores/TimelineEventStore.js
index 664958e6..8ff445f0 100644
--- a/src/matrix/storage/idb/stores/TimelineEventStore.js
+++ b/src/matrix/storage/idb/stores/TimelineEventStore.js
@@ -16,7 +16,7 @@ limitations under the License.
 
 import {EventKey} from "../../../room/timeline/EventKey.js";
 import { StorageError } from "../../common";
-import { encodeUint32 } from "../utils.js";
+import { encodeUint32 } from "../utils";
 import {KeyLimits} from "../../common";
 
 function encodeKey(roomId, fragmentId, eventIndex) {
diff --git a/src/matrix/storage/idb/stores/TimelineFragmentStore.js b/src/matrix/storage/idb/stores/TimelineFragmentStore.js
index 208b7300..07a8ff42 100644
--- a/src/matrix/storage/idb/stores/TimelineFragmentStore.js
+++ b/src/matrix/storage/idb/stores/TimelineFragmentStore.js
@@ -16,7 +16,7 @@ limitations under the License.
 
 import { StorageError } from "../../common";
 import {KeyLimits} from "../../common";
-import { encodeUint32 } from "../utils.js";
+import { encodeUint32 } from "../utils";
 
 function encodeKey(roomId, fragmentId) {
     return `${roomId}|${encodeUint32(fragmentId)}`;
diff --git a/src/matrix/storage/idb/utils.js b/src/matrix/storage/idb/utils.ts
similarity index 100%
rename from src/matrix/storage/idb/utils.js
rename to src/matrix/storage/idb/utils.ts
diff --git a/src/platform/web/legacy-polyfill.js b/src/platform/web/legacy-polyfill.js
index ea2461f7..45628f2c 100644
--- a/src/platform/web/legacy-polyfill.js
+++ b/src/platform/web/legacy-polyfill.js
@@ -16,7 +16,7 @@ limitations under the License.
 
 // polyfills needed for IE11
 import Promise from "../../../lib/es6-promise/index.js";
-import {checkNeedsSyncPromise} from "../../matrix/storage/idb/utils.js";
+import {checkNeedsSyncPromise} from "../../matrix/storage/idb/utils";
 
 if (typeof window.Promise === "undefined") {
     window.Promise = Promise;