diff --git a/.eslintrc.cjs b/.eslintrc.cjs
index 5b94578..06fdc32 100644
--- a/.eslintrc.cjs
+++ b/.eslintrc.cjs
@@ -12,6 +12,7 @@ module.exports = {
     "@typescript-eslint/explicit-module-boundary-types": "off",
     "@typescript-eslint/no-explicit-any": "off",
     "@typescript-eslint/no-unused-vars": ["off", { argsIgnorePattern: "^_" }],
+    "@typescript-eslint/no-non-null-assertion": "off",
   },
   env: {
     browser: true,
diff --git a/src/auth.ts b/src/auth.ts
index b57e3aa..edecf04 100644
--- a/src/auth.ts
+++ b/src/auth.ts
@@ -115,8 +115,7 @@ export class Auth {
     }
 
     const jwt = this.signToken(token);
-    console.log(jwt);
-    const redirect = await this.getRedirectUrl(host, redirectUrl);
+    const redirect = await this.getRedirectUrl(host, redirectUrl ?? undefined);
 
     return {
       status: 302,
@@ -158,9 +157,9 @@ export class Auth {
 
     const match = path.match(/\/api\/auth\/(?<method>signin|callback)\/(?<provider>\w+)/);
 
-    if (match) {
+    if (match && match.groups) {
       const provider = this.config?.providers?.find(
-        (provider) => provider.id === match.groups.provider,
+        (provider) => provider.id === match.groups!.provider,
       );
       if (provider) {
         if (match.groups.method === "signin") {
@@ -170,6 +169,11 @@ export class Auth {
         }
       }
     }
+
+    return {
+      status: 404,
+      body: "Not found.",
+    };
   }
 
   get: RequestHandler = async (request) => {
diff --git a/src/client/signIn.ts b/src/client/signIn.ts
index be97123..3bec5a7 100644
--- a/src/client/signIn.ts
+++ b/src/client/signIn.ts
@@ -19,17 +19,19 @@ export async function signIn(provider: string, data?: any, config?: SignInConfig
     return await res.json();
   }
 
-  let redirectUrl: string;
+  let redirectUrl: string | undefined;
   if (config?.redirectUrl) {
     redirectUrl = config.redirectUrl;
   } else {
-    let $val: Page;
+    let $val: Page | undefined;
     page.subscribe(($) => ($val = $))();
-    redirectUrl = `${$val.host}${$val.path}?${$val.query}`;
+    if ($val) {
+      redirectUrl = `${$val.host}${$val.path}?${$val.query}`;
+    }
   }
 
   const queryData = {
-    redirect: redirectUrl,
+    redirect: redirectUrl ?? "/",
   };
   const query = new URLSearchParams(queryData);
   const path = `/api/auth/login/${provider}?${query}`;
diff --git a/src/providers/base.ts b/src/providers/base.ts
index 4d84d54..7671264 100644
--- a/src/providers/base.ts
+++ b/src/providers/base.ts
@@ -11,7 +11,7 @@ export abstract class Provider<T extends ProviderConfig = ProviderConfig> {
   id: string;
 
   constructor(protected readonly config: T) {
-    this.id = config.id;
+    this.id = config.id!;
   }
 
   getUri(host: string, path: string) {
diff --git a/src/providers/facebook.ts b/src/providers/facebook.ts
index c012b64..594d819 100644
--- a/src/providers/facebook.ts
+++ b/src/providers/facebook.ts
@@ -28,7 +28,7 @@ export class FacebookAuthProvider extends OAuth2Provider<FacebookAuthProviderCon
 
     const data = {
       client_id: this.config.clientId,
-      scope: this.config.scope,
+      scope: this.config.scope!,
       redirect_uri: this.getCallbackUri(host),
       state,
     };
@@ -69,7 +69,7 @@ export class FacebookAuthProvider extends OAuth2Provider<FacebookAuthProviderCon
 
     const data = {
       access_token: tokens.access_token,
-      fields: this.config.userProfileFields,
+      fields: this.config.userProfileFields!,
     };
 
     const res = await fetch(`${endpoint}?${new URLSearchParams(data)}`);
diff --git a/src/providers/google.ts b/src/providers/google.ts
index 0f44168..bb0bfd8 100644
--- a/src/providers/google.ts
+++ b/src/providers/google.ts
@@ -23,7 +23,7 @@ export class GoogleOAuthProvider extends OAuth2Provider<GoogleOAuthProviderConfi
   }
 
   async getProviderMetadata() {
-    const res = await fetch(this.config.discoveryDocument);
+    const res = await fetch(this.config.discoveryDocument!);
     const metadata = await res.json();
     return metadata;
   }
@@ -39,7 +39,7 @@ export class GoogleOAuthProvider extends OAuth2Provider<GoogleOAuthProviderConfi
     const data = {
       response_type: "code",
       client_id: this.config.clientId,
-      scope: this.config.scope,
+      scope: this.config.scope!,
       redirect_uri: this.getCallbackUri(host),
       state,
       login_hint: "example@provider.com",
diff --git a/src/providers/oauth2.ts b/src/providers/oauth2.ts
index 16aa1a9..463ef5c 100644
--- a/src/providers/oauth2.ts
+++ b/src/providers/oauth2.ts
@@ -35,7 +35,7 @@ export abstract class OAuth2Provider<T extends OAuth2ProviderConfig> extends Pro
 
   getStateValue(query: URLSearchParams, name: string) {
     if (query.get("state")) {
-      const state = Buffer.from(query.get("state"), "base64").toString();
+      const state = Buffer.from(query.get("state")!, "base64").toString();
       return state
         .split(",")
         .find((state) => state.startsWith(`${name}=`))
@@ -47,7 +47,7 @@ export abstract class OAuth2Provider<T extends OAuth2ProviderConfig> extends Pro
     const code = query.get("code");
     const redirect = this.getStateValue(query, "redirect");
 
-    const tokens = await this.getTokens(code, this.getCallbackUri(host));
+    const tokens = await this.getTokens(code!, this.getCallbackUri(host));
     let user = await this.getUserProfile(tokens);
 
     if (this.config.profile) {
diff --git a/src/providers/reddit.ts b/src/providers/reddit.ts
index 240a502..885ab3d 100644
--- a/src/providers/reddit.ts
+++ b/src/providers/reddit.ts
@@ -79,8 +79,8 @@ export class RedditOAuthProvider extends OAuth2Provider<RedditOAuthProviderConfi
       response_type: "code",
       state,
       redirect_uri: this.getCallbackUri(host),
-      duration: this.config.duration,
-      scope: this.config.scope,
+      duration: this.config.duration!,
+      scope: this.config.scope!,
     };
 
     const url = `${endpoint}?${new URLSearchParams(data)}`;
diff --git a/src/providers/twitter.ts b/src/providers/twitter.ts
index 934beac..8ccf167 100644
--- a/src/providers/twitter.ts
+++ b/src/providers/twitter.ts
@@ -75,7 +75,7 @@ export class TwitterAuthProvider extends OAuth2Provider<TwitterAuthProviderConfi
     const oauthVerifier = query.get("oauth_verifier");
     const redirect = this.getStateValue(query, "redirect");
 
-    const tokens = await this.getTokens(oauthToken, oauthVerifier);
+    const tokens = await this.getTokens(oauthToken!, oauthVerifier!);
     let user = await this.getUserProfile(tokens);
 
     if (this.config.profile) {
diff --git a/tsconfig.json b/tsconfig.json
index 4c75c72..b2f2807 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,14 +1,17 @@
 {
   "compilerOptions": {
-    "target": "es5",
+    "target": "es2017",
     "module": "es6",
     "moduleResolution": "node",
+    "strict": true,
+    "noImplicitAny": false,
     "declaration": true,
     "removeComments": true,
     "emitDecoratorMetadata": true,
     "experimentalDecorators": true,
+    "skipLibCheck": true,
+    "esModuleInterop": true,
     "allowSyntheticDefaultImports": true,
-    "target": "es2017",
     "sourceMap": true,
     "outDir": "./dist",
     "baseUrl": "./",