diff --git a/acl/acl-mongodbBackend-tests.ts b/acl/acl-mongodbBackend-tests.ts
index 080bfbf42..31411b65c 100644
--- a/acl/acl-mongodbBackend-tests.ts
+++ b/acl/acl-mongodbBackend-tests.ts
@@ -14,3 +14,4 @@ acl.allow('guest', 'blogs', 'view');
 
 // allow function accepts arrays as any parameter
 acl.allow('member', 'blogs', ['edit','view', 'delete']);
+
diff --git a/acl/acl-mongodbBackend.d.ts b/acl/acl-mongodbBackend.d.ts
index 48fe6f135..8dbfb7e90 100644
--- a/acl/acl-mongodbBackend.d.ts
+++ b/acl/acl-mongodbBackend.d.ts
@@ -13,7 +13,7 @@ declare module "acl" {
     mongodbBackend: MongodbBackendStatic;
   }
 
-  interface MongodbBackend extends Backend<ErrCallback> { }
+  interface MongodbBackend extends Backend<Callback> { }
   interface MongodbBackendStatic {
     new(db: mongo.Db, prefix: string, useSingle: boolean): MongodbBackend;
     new(db: mongo.Db, prefix: string): MongodbBackend;
diff --git a/acl/acl-redisBackend-test.ts b/acl/acl-redisBackend-test.ts
index ce1036528..e1bf29af4 100644
--- a/acl/acl-redisBackend-test.ts
+++ b/acl/acl-redisBackend-test.ts
@@ -1,4 +1,4 @@
-/// <reference path='./acl-redisBackend.d.ts'/>
+/// <reference path='acl-redisBackend.d.ts'/>
 
 // https://github.com/OptimalBits/node_acl/blob/master/Readme.md
 import Acl = require('acl');
diff --git a/acl/acl.d.ts b/acl/acl.d.ts
index f98bcb1ae..5d0498fed 100644
--- a/acl/acl.d.ts
+++ b/acl/acl.d.ts
@@ -10,14 +10,14 @@ declare module "acl" {
   import http = require('http');
   import Promise = require("bluebird");
 
-  type Func = ()=>any;
+  type strings = string|string[];
   type Value = string|number;
   type Values = Value|Value[];
-  type strings = string|string[];
-  type ErrCallback = (err: Error) => any;
+  type Action = () => any;
+  type Callback = (err: Error) => any;
   type AnyCallback = (err: Error, obj: any) => any;
   type AllowedCallback = (err: Error, allowed: boolean) => any;
-  type GetUserId = (req: http.ServerRequest, res: http.ServerResponse) => any;
+  type GetUserId = (req: http.ServerRequest, res: http.ServerResponse) => Value;
 
   interface AclStatic {
     new (backend: Backend<any>, logger: Logger, options: Option): Acl;
@@ -31,19 +31,19 @@ declare module "acl" {
   }
 
   interface Acl {
-    addUserRoles: (userId: Value, roles: strings, cb?: ErrCallback) => Promise<void>;
-    removeUserRoles: (userId: Value, roles: strings, cb?: ErrCallback) => Promise<void>;
+    addUserRoles: (userId: Value, roles: strings, cb?: Callback) => Promise<void>;
+    removeUserRoles: (userId: Value, roles: strings, cb?: Callback) => Promise<void>;
     userRoles: (userId: Value, cb?: (err: Error, roles: string[])=>any) => Promise<string[]>;
     roleUsers: (role: Value, cb?: (err: Error, users: Values)=>any) => Promise<any>;
     hasRole: (userId: Value, role: string, cb?: (err: Error, isInRole: boolean)=>any) => Promise<boolean>;
-    addRoleParents: (role: string, parents: Values, cb?: ErrCallback) => Promise<void>;
-    removeRole: (role: string, cb?: ErrCallback) => Promise<void>;
-    removeResource: (resource: string, cb?: ErrCallback) => Promise<void>;
+    addRoleParents: (role: string, parents: Values, cb?: Callback) => Promise<void>;
+    removeRole: (role: string, cb?: Callback) => Promise<void>;
+    removeResource: (resource: string, cb?: Callback) => Promise<void>;
     allow: {
-      (roles: Values, resources: strings, permissions: strings, cb?: ErrCallback): Promise<void>;
+      (roles: Values, resources: strings, permissions: strings, cb?: Callback): Promise<void>;
       (aclSets: AclSet|AclSet[]): Promise<void>;
     }
-    removeAllow: (role: string, resources: strings, permissions: strings, cb?: ErrCallback) => Promise<void>;
+    removeAllow: (role: string, resources: strings, permissions: strings, cb?: Callback) => Promise<void>;
     removePermissions: (role: string, resources: strings, permissions: strings, cb?: Function) => Promise<void>;
     allowedPermissions: (userId: Value, resources: strings, cb?: AnyCallback) => Promise<void>;
     isAllowed: (userId: Value, resources: strings, permissions: strings, cb?: AllowedCallback) => Promise<boolean>;
@@ -76,15 +76,23 @@ declare module "acl" {
     permissions: strings;
   }
 
+  interface MemoryBackend extends Backend<Action[]> { }
+  interface MemoryBackendStatic {
+    new(): MemoryBackend;
+  }
+
+  //
+  // For internal use
+  //
   interface Backend<T> {
     begin: () => T;
-    end: (transaction: T, cb?: Func) => void;
-    clean: (cb?: Func) => void;
-    get: (bucket: string, key: Value, cb?: Func) => void;
-    union: (bucket: string, keys: Value[], cb?: Func) => void;
-    add: (transaction: T, bucket: string, key: Value, values: Value|Value[]) => void;
+    end: (transaction: T, cb?: Action) => void;
+    clean: (cb?: Action) => void;
+    get: (bucket: string, key: Value, cb?: Action) => void;
+    union: (bucket: string, keys: Value[], cb?: Action) => void;
+    add: (transaction: T, bucket: string, key: Value, values: Values) => void;
     del: (transaction: T, bucket: string, keys: Value[]) => void;
-    remove: (transaction: T, bucket: string, key: Value, values: Value|Value[]) => void;
+    remove: (transaction: T, bucket: string, key: Value, values: Values) => void;
 
     endAsync: Function; //TODO: Give more specific function signature
     getAsync: Function;
@@ -92,11 +100,6 @@ declare module "acl" {
     unionAsync: Function;
   }
 
-  interface MemoryBackend extends Backend<Func[]> { }
-  interface MemoryBackendStatic {
-    new(): MemoryBackend;
-  }
-
   interface Contract {
     (args: IArguments): Contract|NoOp;
     debug: boolean;