diff --git a/CHANGELOG.md b/CHANGELOG.md
index b3b03de..cd81cf7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # log4js-node changelog
 
+## 4.1.1
+* [Add missing types for addLevels](https://github.com/log4js-node/log4js-node/pull/867) - thanks [@Ivkaa](https://github.com/Ivkaa)
+* [Allow any return type for layout function](https://github.com/log4js-node/log4js-node/pull/845) - thanks [@xinbenlv](https://github.com/xinbenlv)
+
 ## 4.1.0
 
 * Updated streamroller to 1.0.4, to fix a bug where the inital size of an existing file was ignored when appending
diff --git a/test/tap/configuration-validation-test.js b/test/tap/configuration-validation-test.js
index 6a0a6aa..39c7789 100644
--- a/test/tap/configuration-validation-test.js
+++ b/test/tap/configuration-validation-test.js
@@ -297,6 +297,11 @@ test('log4js configuration validation', (batch) => {
     sandboxConfig.requires[
       `${path.join(mainPath, '../../node_modules/nyc/bin/cheese')}`
     ] = testAppender('correct', result);
+    // in node v6, there's an extra layer of node modules for some reason, so add this one to work around it
+    sandboxConfig.requires[
+      `${path.join(mainPath, '../../node_modules/tap/node_modules/nyc/bin/cheese')}`
+    ] = testAppender('correct', result);
+
     const sandboxedLog4js = sandbox.require('../../lib/log4js', sandboxConfig);
 
     sandboxedLog4js.configure({
diff --git a/types/log4js.d.ts b/types/log4js.d.ts
index 7ae36f5..c7f38d6 100644
--- a/types/log4js.d.ts
+++ b/types/log4js.d.ts
@@ -17,7 +17,7 @@ export function getLogger(category?: string): Logger;
 export function configure(filename: string): Log4js;
 export function configure(config: Configuration): Log4js;
 
-export function addLayout(name: string, config: (a: any) => (logEvent: LoggingEvent) => string): void;
+export function addLayout(name: string, config: (a: any) => (logEvent: LoggingEvent) => any): void;
 
 export function connectLogger(logger: Logger, options: { format?: Format; level?: string; nolog?: any; statusRules?: any[] }): any; // express.Handler;
 
@@ -264,6 +264,7 @@ export interface Levels {
   OFF: Level;
   levels: Level[];
   getLevel(level: string): Level;
+  addLevels(customLevels: object): void;
 }
 
 export interface Configuration {