diff --git a/examples/pm2.js b/examples/pm2.js
index e3df67e..5555323 100644
--- a/examples/pm2.js
+++ b/examples/pm2.js
@@ -9,7 +9,8 @@ log4js.configure({
   categories: {
     default: { appenders: ['out'], level: 'info' }
   },
-  pm2: true
+  pm2: true,
+  pm2InstanceVar: 'INSTANCE_ID'
 });
 
 const logger = log4js.getLogger('app');
diff --git a/examples/pm2.json b/examples/pm2.json
new file mode 100644
index 0000000..45ba25b
--- /dev/null
+++ b/examples/pm2.json
@@ -0,0 +1,9 @@
+{ "apps": [
+  { "name": "testing",
+    "script": "pm2.js",
+    "instances": 0,
+    "instance_var": "INSTANCE_ID",
+    "exec_mode": "cluster"
+    }
+    ]
+  }
diff --git a/lib/configuration.js b/lib/configuration.js
index 2339117..40c5c42 100644
--- a/lib/configuration.js
+++ b/lib/configuration.js
@@ -76,6 +76,10 @@ class Configuration {
       debug(`DEPRECATION: Appender ${config.type} exports a shutdown function.`);
     }
 
+    debug(`cluster.isMaster ? ${cluster.isMaster}`);
+    debug(`pm2 enabled ? ${this.pm2}`);
+    debug(`pm2InstanceVar = ${this.pm2InstanceVar}`);
+    debug(`process.env[${this.pm2InstanceVar}] = ${process.env[this.pm2InstanceVar]}`);
     if (cluster.isMaster || (this.pm2 && process.env[this.pm2InstanceVar] === '0')) {
       return appenderModule.configure(
         config,
diff --git a/test/tap/configuration-validation-test.js b/test/tap/configuration-validation-test.js
index b0fba77..d262f32 100644
--- a/test/tap/configuration-validation-test.js
+++ b/test/tap/configuration-validation-test.js
@@ -303,7 +303,7 @@ test('log4js configuration validation', (batch) => {
           '/var/lib/cheese/cheese': testAppender('correct'),
         },
         globals: {
-          process: { cwd: () => '/var/lib/cheese' }
+          process: { cwd: () => '/var/lib/cheese', env: {} }
         }
       }
     );