diff --git a/src/observable/list/common.ts b/src/observable/list/common.ts
index 8dbf7873..c67a841b 100644
--- a/src/observable/list/common.ts
+++ b/src/observable/list/common.ts
@@ -14,9 +14,10 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
+import {BaseObservableList} from "./BaseObservableList";
 
 /* inline update of item in collection backed by array, without replacing the preexising item */
-export function findAndUpdateInArray(predicate, array, observable, updater) {
+export function findAndUpdateInArray<T>(predicate: (value: T) => boolean, array: T[], observable: BaseObservableList<T>, updater: (value: T) => any | false) {
     const index = array.findIndex(predicate);
     if (index !== -1) {
         const value = array[index];
@@ -29,4 +30,4 @@ export function findAndUpdateInArray(predicate, array, observable, updater) {
         return true;
     }
     return false;
-}
\ No newline at end of file
+}