diff --git a/src/index.ts b/src/index.ts
index 2e4df84..1cd2c9b 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -13,7 +13,7 @@ class Menu {
   #showMenu() {
     const options = this.#optionsContent.map((fragment) => {
       const option = document.createElement('span');
-      option.setAttribute(TOKENS.get('optionAttr'), '');
+      option.setAttribute(TOKENS.get('optionAttr') as string, '');
       option.append(fragment);
       return option;
     });
diff --git a/tsconfig.json b/tsconfig.json
index b5b382e..1598acc 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -6,6 +6,8 @@
     "declaration": true,
     "declarationMap": true,
     "allowSyntheticDefaultImports":true,
+    "strictNullChecks":true,
+    "strictPropertyInitialization":true,
     "outDir": "./dist"
   },
   "include": ["src/**/*"]