diff --git a/apps/automated/src/data/observable-array-tests.ts b/apps/automated/src/data/observable-array-tests.ts
index d5967f722..1ec46cf0b 100644
--- a/apps/automated/src/data/observable-array-tests.ts
+++ b/apps/automated/src/data/observable-array-tests.ts
@@ -16,7 +16,8 @@ export const test_ObservableArray_shouldCopySourceArrayItems = function () {
 export const test_ObservableArray_shouldCopyMultipleItemsAsSource = function () {
 	// >> observable-array-arguments
 	const sa = [1, 2, 3];
-	const array = new ObservableArray(...sa);
+	// Avoid appending items using spread operator as it will skip argument type check
+	const array = new ObservableArray(1, 2, 3);
 	// << observable-array-arguments
 
 	TKUnit.assertEqual(array.length, 3, 'ObservableArray length should be 3');
diff --git a/packages/core/data/observable-array/index.ts b/packages/core/data/observable-array/index.ts
index 595b0b4d0..500950a4a 100644
--- a/packages/core/data/observable-array/index.ts
+++ b/packages/core/data/observable-array/index.ts
@@ -50,10 +50,22 @@ export class ObservableArray<T> extends Observable {
 	private _addArgs: ChangedData<T>;
 	private _deleteArgs: ChangedData<T>;
 
+	/**
+	 * Create ObservableArray<T> with specified length.
+	 */
+	constructor(arrayLength?: number);
+
 	/**
 	 * Create ObservableArray<T> from source Array<T>.
 	 */
-	constructor(args?: T[] | number) {
+	constructor(items: T[]);
+
+	/**
+	 * Create ObservableArray<T> from T items.
+	 */
+	constructor(...items: T[]);
+
+	constructor(_args?: any) {
 		super();
 
 		if (arguments.length === 1 && Array.isArray(arguments[0])) {