diff --git a/lib/layouts.js b/lib/layouts.js
index 389e7aa..270f336 100644
--- a/lib/layouts.js
+++ b/lib/layouts.js
@@ -145,7 +145,7 @@ function messagePassThroughLayout (loggingEvent) {
  */
 function patternLayout (pattern, tokens) {
   var TTCC_CONVERSION_PATTERN  = "%r %p %c - %m%n";
-  var regex = /%(-?[0-9]+)?(\.?[0-9]+)?([\[\]cdhmnprx%])(\{([^\}]+)\})?|([^%]+)/;
+  var regex = /%(-?[0-9]+)?(\.?[0-9]+)?([\[\]cdhmnprzx%])(\{([^\}]+)\})?|([^%]+)/;
   
   pattern = pattern || TTCC_CONVERSION_PATTERN;