diff --git a/types/aes-js/aes-js-tests.ts b/types/aes-js/aes-js-tests.ts
index 4f9d582630..9379fda89e 100644
--- a/types/aes-js/aes-js-tests.ts
+++ b/types/aes-js/aes-js-tests.ts
@@ -8,3 +8,6 @@ const ecb = new aesjs.ModeOfOperation.ecb(key);
 ecb.decrypt(ecb.encrypt(data));
 
 const hex: string = aesjs.utils.hex.fromBytes(data);
+
+const ctr = new aesjs.ModeOfOperation.ctr(key, new aesjs.Counter([]));
+ctr.encrypt(data);
diff --git a/types/aes-js/index.d.ts b/types/aes-js/index.d.ts
index 142e03f7d9..e6bebdb9df 100644
--- a/types/aes-js/index.d.ts
+++ b/types/aes-js/index.d.ts
@@ -19,7 +19,7 @@ export class AES {
  * @param initialValue The Counter initial value.
  */
 export class Counter {
-    constructor(initialValue: number)
+    constructor(initialValue: number | ByteSource)
     setValue(value: number): void;
     setBytes(bytes: ByteSource): void;
     increment(): void;