diff --git a/.gitignore b/.gitignore
index 2c6ebfe..f1cc977 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 node_modules
 .envrc
-dist
 .vscode
+dist
+src/test.ts
diff --git a/package.json b/package.json
index 8852a55..460c064 100644
--- a/package.json
+++ b/package.json
@@ -13,6 +13,7 @@
     "node": ">=8"
   },
   "main": "dist/index.js",
+  "types": "dist/index.d.ts",
   "scripts": {
     "add-contributor": "all-contributors add",
     "fmt": "prettier --write '**/*.{ts,js,json,md}'",
diff --git a/src/index.ts b/src/index.ts
index e7e3cb8..481263f 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -54,8 +54,8 @@ const HASH_SECRET =
   '28c1fdd170a5204386cb1313c7077b34f83e4aaf4aa829ce78c231e05b0bae2c'
 const filter = 'for_ios'
 
-export default class PixivApp<CamelcaseKeys extends boolean> {
-  camelcaseKeys = true as CamelcaseKeys
+export default class PixivApp<CamelcaseKeys extends boolean = true> {
+  camelcaseKeys: CamelcaseKeys
   username: string | undefined
   password: string | undefined
   refreshToken: string
@@ -76,6 +76,8 @@ export default class PixivApp<CamelcaseKeys extends boolean> {
     this._once = false
     if (options) {
       this.camelcaseKeys = Boolean(options.camelcaseKeys) as CamelcaseKeys
+    } else {
+      this.camelcaseKeys = true as CamelcaseKeys
     }
   }
 
diff --git a/tsconfig.json b/tsconfig.json
index d978a9f..e083f8d 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -3,7 +3,8 @@
   "compilerOptions": {
     "outDir": "dist",
     "strict": true,
-    "noImplicitAny": true
+    "noImplicitAny": true,
+    "declaration": true
   },
   "include": ["src", "declarations.d.ts"]
 }