diff --git a/src/observable/list/AsyncMappedList.js b/src/observable/list/AsyncMappedList.js
index 604d8e94..9af1f95a 100644
--- a/src/observable/list/AsyncMappedList.js
+++ b/src/observable/list/AsyncMappedList.js
@@ -15,7 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseMappedList, runAdd, runUpdate, runRemove, runMove, runReset} from "./BaseMappedList.js";
+import {BaseMappedList, runAdd, runUpdate, runRemove, runMove, runReset} from "./BaseMappedList";
 
 export class AsyncMappedList extends BaseMappedList {
     constructor(sourceList, mapper, updater, removeCallback) {
diff --git a/src/observable/list/BaseMappedList.js b/src/observable/list/BaseMappedList.ts
similarity index 100%
rename from src/observable/list/BaseMappedList.js
rename to src/observable/list/BaseMappedList.ts
diff --git a/src/observable/list/MappedList.js b/src/observable/list/MappedList.js
index dbd64921..c799fcff 100644
--- a/src/observable/list/MappedList.js
+++ b/src/observable/list/MappedList.js
@@ -15,7 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import {BaseMappedList, runAdd, runUpdate, runRemove, runMove, runReset} from "./BaseMappedList.js";
+import {BaseMappedList, runAdd, runUpdate, runRemove, runMove, runReset} from "./BaseMappedList";
 
 export class MappedList extends BaseMappedList {
     onSubscribeFirst() {