diff --git a/types/morgan/index.d.ts b/types/morgan/index.d.ts
index 4a5afe4df5..09a9f21f57 100644
--- a/types/morgan/index.d.ts
+++ b/types/morgan/index.d.ts
@@ -24,7 +24,7 @@ declare namespace morgan {
      */
     export interface Morgan {
         /***
-         * Create a new morgan logger middleware function using the given format and options. The format argument may be a string of a predefined name (see below for the names), 
+         * Create a new morgan logger middleware function using the given format and options. The format argument may be a string of a predefined name (see below for the names),
          * or a string of a format string containing defined tokens.
          * @param format
          * @param options
@@ -69,7 +69,7 @@ declare namespace morgan {
         (format: 'tiny', options?: Options): express.RequestHandler;
 
         /***
-         * Create a new morgan logger middleware function using the given format and options. The format argument may be a  
+         * Create a new morgan logger middleware function using the given format and options. The format argument may be a
          * custom format function which adheres to the signature.
          * @param format
          * @param options
@@ -152,7 +152,7 @@ declare namespace morgan {
 }
 
 /***
-     * Create a new morgan logger middleware function using the given format and options. The format argument may be a string of a predefined name (see below for the names), 
+     * Create a new morgan logger middleware function using the given format and options. The format argument may be a string of a predefined name (see below for the names),
      * or a string of a format string containing defined tokens.
  * @param format
  * @param options
@@ -200,11 +200,11 @@ declare function morgan(format: 'short', options?: morgan.Options): express.Requ
 declare function morgan(format: 'tiny', options?: morgan.Options): express.RequestHandler;
 
 /***
- * Create a new morgan logger middleware function using the given format and options. The format argument may be a  
+ * Create a new morgan logger middleware function using the given format and options. The format argument may be a
  * custom format function which adheres to the signature.
  * @param format
  * @param options
  */
-declare function morgan(custom: (req: express.Request, res: express.Response) => string): express.RequestHandler
+declare function morgan(format: morgan.FormatFn, options?: morgan.Options): express.RequestHandler
 
 export = morgan;
diff --git a/types/morgan/morgan-tests.ts b/types/morgan/morgan-tests.ts
index 3bbd7c33ee..50a185fdd4 100644
--- a/types/morgan/morgan-tests.ts
+++ b/types/morgan/morgan-tests.ts
@@ -15,16 +15,37 @@ morgan('tiny')
 morgan(':remote-addr :method :url')
 
 morgan('combined', {
-    buffer: true,
-    immediate: true,
-    skip: function (req, res) { return res.statusCode < 400 },
-    stream: {
-    	write: (str: string) => {
-        	console.log(str);
-    	}
+  buffer: true,
+  immediate: true,
+  skip: function (req, res) { return res.statusCode < 400 },
+  stream: {
+    write: (str: string) => {
+      console.log(str);
     }
+  }
 });
 
+// a custom format function
+morgan((tokens, req, res) => {
+  return [
+    tokens.method(req, res),
+    tokens.url(req, res),
+    tokens.status(req, res),
+    tokens.res(req, res, 'content-length'), '-',
+    tokens['response-time'](req, res), 'ms'
+  ].join(' ');
+});
+// a custom format function with options
+morgan((_tokens, _req, _res) => "", {
+  buffer: true,
+  immediate: true,
+  skip: function (req, res) { return res.statusCode < 400 },
+  stream: {
+    write: (str: string) => {
+      console.log(str);
+    }
+  }
+});
 
 // test interface definition for morgan
 
@@ -46,7 +67,7 @@ interface IExtendedFormatFn extends morgan.FormatFn {
 
 
 var developmentExtendedFormatLine : IExtendedFormatFn = function(tokens, req, res):string {
-    
+
   // get the status code if response written
   var status = res.statusCode
     ? res.statusCode