diff --git a/lib/layouts.js b/lib/layouts.js
index be5681c..1a1f094 100644
--- a/lib/layouts.js
+++ b/lib/layouts.js
@@ -213,7 +213,7 @@ function patternLayout (pattern, tokens) {
   }
 
   function pid(loggingEvent) {
-    if (loggingEvent.pid) {
+    if (loggingEvent && loggingEvent.pid) {
       return loggingEvent.pid;
     } else {
       return process.pid;