diff --git a/types/koa-sslify/index.d.ts b/types/koa-sslify/index.d.ts
index 0bf6c0a1ff..418b330586 100644
--- a/types/koa-sslify/index.d.ts
+++ b/types/koa-sslify/index.d.ts
@@ -1,25 +1,80 @@
-// Type definitions for koa-sslify 2.1
+// Type definitions for koa-sslify 4.0
 // Project: https://github.com/turboMaCk/koa-sslify#readme
 // Definitions by: Matthew Bull <https://github.com/wingsbob>
+//                 Mihkel Sokk <https://github.com/msokk>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.3
 
-import * as koa from 'koa';
+import * as koa from "koa";
 
 declare namespace sslify {
-  interface Options {
-    trustProtoHeader?: boolean;
-    trustAzureHeader?: boolean;
-    port?: number;
-    hostname?: string;
-    ignoreUrl?: boolean;
-    temporary?: boolean;
-    redirectMethods?: string[];
-    internalRedirectMethods?: string[];
-    specCompliantDisallow?: boolean;
-  }
+    interface Options {
+        /**
+         * Function used to test if request is secure
+         */
+        resolver?: (ctx: koa.Context) => boolean;
+        /**
+         * Hostname for redirect (uses request host if not set)
+         */
+        hostname?: string;
+        /**
+         * Port of HTTPS server
+         */
+        port?: number;
+        /**
+         * Avoid :443 port in redirect url
+         */
+        skipDefaultPort?: boolean;
+        /**
+         * Ignore url path (redirect to domain)
+         */
+        ignoreUrl?: boolean;
+        /**
+         * Temporary mode (use 307 Temporary Redirect)
+         */
+        temporary?: boolean;
+        /**
+         * Whitelist methods that should be redirected
+         */
+        redirectMethods?: string[];
+        /**
+         * Status returned for disallowed methods
+         */
+        disallowStatus?: number;
+    }
+
+    /**
+     * Default HTTPS resolver
+     * This works when using node.js TLS support
+     */
+    function httpsResolver(ctx: koa.Context): boolean;
+
+    /**
+     * x-forwarded-proto header resolver
+     * common for heroku gcp (ingress) etc
+     */
+    function xForwardedProtoResolver(ctx: koa.Context): boolean;
+
+    /**
+     * Azure resolver
+     * Azure is using `x-att-ssl` header
+     */
+    function azureResolver(ctx: koa.Context): boolean;
+
+    /**
+     * Custom proto header factory
+     */
+    function customProtoHeaderResolver(
+        header: string
+    ): (ctx: koa.Context) => boolean;
+
+    /**
+     * Resolver for `Forwarded` header
+     * see https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Forwarded
+     */
+    function forwardedResolver(ctx: koa.Context): boolean;
 }
 
-declare function sslify(options: sslify.Options): koa.Middleware;
+declare function sslify(options?: sslify.Options): koa.Middleware;
 
 export = sslify;
diff --git a/types/koa-sslify/koa-sslify-tests.ts b/types/koa-sslify/koa-sslify-tests.ts
index c8dae23bb4..7c87c7c705 100644
--- a/types/koa-sslify/koa-sslify-tests.ts
+++ b/types/koa-sslify/koa-sslify-tests.ts
@@ -1,40 +1,50 @@
 import Koa = require('koa');
 import sslify = require('koa-sslify');
 
+new Koa().use(sslify());
+
 new Koa().use(sslify({}));
 
 new Koa().use(sslify({
-  trustAzureHeader: true,
+    resolver: sslify.xForwardedProtoResolver,
 }));
 
 new Koa().use(sslify({
-  trustProtoHeader: true,
+    resolver: sslify.azureResolver,
 }));
 
 new Koa().use(sslify({
-  specCompliantDisallow: true,
+    resolver: sslify.customProtoHeaderResolver('x-protocol'),
 }));
 
 new Koa().use(sslify({
-  port: 1234,
+    resolver: sslify.forwardedResolver,
 }));
 
 new Koa().use(sslify({
-  hostname: 'my-host',
+    disallowStatus: 405,
 }));
 
 new Koa().use(sslify({
-  temporary: false,
+    port: 1234,
 }));
 
 new Koa().use(sslify({
-  internalRedirectMethods: ['GET'],
+    hostname: 'my-host',
 }));
 
 new Koa().use(sslify({
-  redirectMethods: ['GET'],
+    temporary: false,
 }));
 
 new Koa().use(sslify({
-  ignoreUrl: true,
+    redirectMethods: ['GET'],
+}));
+
+new Koa().use(sslify({
+    skipDefaultPort: false,
+}));
+
+new Koa().use(sslify({
+    ignoreUrl: true,
 }));
diff --git a/types/koa-sslify/tsconfig.json b/types/koa-sslify/tsconfig.json
index 775b453de9..8c1672161b 100644
--- a/types/koa-sslify/tsconfig.json
+++ b/types/koa-sslify/tsconfig.json
@@ -1,23 +1,16 @@
 {
     "compilerOptions": {
         "module": "commonjs",
-        "lib": [
-            "es6"
-        ],
+        "lib": ["es6"],
         "noImplicitAny": true,
         "noImplicitThis": true,
         "strictNullChecks": true,
         "strictFunctionTypes": true,
         "baseUrl": "../",
-        "typeRoots": [
-            "../"
-        ],
+        "typeRoots": ["../"],
         "types": [],
         "noEmit": true,
         "forceConsistentCasingInFileNames": true
     },
-    "files": [
-        "index.d.ts",
-        "koa-sslify-tests.ts"
-    ]
-}
\ No newline at end of file
+    "files": ["index.d.ts", "koa-sslify-tests.ts"]
+}