diff --git a/src/OptionsNormalizer.ts b/src/OptionsNormalizer.ts
index 978e6fcf..9b6b9fbb 100644
--- a/src/OptionsNormalizer.ts
+++ b/src/OptionsNormalizer.ts
@@ -14,7 +14,7 @@ export class OptionsNormalizer {
      * @returns {IOptions}
      */
     private static unicodeArrayRule (options: IOptions): IOptions {
-        const disabledUnicodeArrayOptions: {[index: string]: boolean} = {
+        const disabledUnicodeArrayOptions: IOptions = {
             encodeUnicodeLiterals: false,
             rotateUnicodeArray: false,
             unicodeArray: false,