diff --git a/lib/AbstractAppender.js b/lib/AbstractAppender.js
index 98391af..13013cd 100644
--- a/lib/AbstractAppender.js
+++ b/lib/AbstractAppender.js
@@ -62,9 +62,9 @@ const AbstractAppender = function(options) {
             return '';
         }
 
-        if (util.isArray( msg )) {
+        if (Array.isArray( msg )) {
             const list = msg.map(function(item) {
-                if (util.isDate( item )) {
+                if (item instanceof Date) {
                     return apdr.formatDate( item );
                 } else {
                     return apdr.formatObject( item );
diff --git a/package-lock.json b/package-lock.json
index 3a4205f..6a2082d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,11 +1,12 @@
 {
   "name": "simple-node-logger",
-  "version": "21.8.11",
+  "version": "21.9.1",
   "lockfileVersion": 2,
   "requires": true,
   "packages": {
     "": {
-      "version": "21.8.11",
+      "name": "simple-node-logger",
+      "version": "21.9.1",
       "license": "Apache-2.0",
       "dependencies": {
         "lodash": "^4.17.12",
diff --git a/package.json b/package.json
index ac335f9..1fd109e 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "simple-node-logger",
-  "version": "21.8.12",
+  "version": "21.9.1",
   "description": "A node console and file logger suitable for small, medium and large production projects.",
   "main": "index.js",
   "repository": {