diff --git a/lib/clustering.js b/lib/clustering.js
index ca49cb5..61c6ff1 100644
--- a/lib/clustering.js
+++ b/lib/clustering.js
@@ -5,7 +5,7 @@ const configuration = require("./configuration");
 let disabled = false;
 let cluster = null;
 try {
-  cluster = require("cluster"); //eslint-disable-line
+  cluster = require("cluster"); // eslint-disable-line
 } catch (e) {
   debug("cluster module not present");
   disabled = true;
@@ -17,7 +17,7 @@ let pm2 = false;
 let pm2InstanceVar = "NODE_APP_INSTANCE";
 
 const isPM2Master = () => pm2 && process.env[pm2InstanceVar] === "0";
-const isMaster = () => disabled || cluster.isMaster || isPM2Master();
+const isMaster = () => disabled || (cluster && cluster.isMaster) || isPM2Master();
 
 const sendToListeners = logEvent => {
   listeners.forEach(l => l(logEvent));
@@ -72,7 +72,7 @@ if (!disabled) {
       // we only want one of the app instances to write logs
       debug("listening for PM2 broadcast messages");
       process.on("message", receiver);
-    } else if (cluster.isMaster) {
+    } else if (cluster && cluster.isMaster) {
       debug("listening for cluster messages");
       cluster.on("message", receiver);
     } else {