diff --git a/lib/appenders/gelf.js b/lib/appenders/gelf.js
index 01544f9..d130bf7 100644
--- a/lib/appenders/gelf.js
+++ b/lib/appenders/gelf.js
@@ -48,13 +48,14 @@ function gelfAppender (layout, host, port, hostname, facility) {
   host = host || 'localhost';
   port = port || 12201;
   hostname = hostname || require('os').hostname();
-  if(facility) {
-    customFields['_facility'] = facility;
-  }
   layout = layout || layouts.messagePassThroughLayout;
 
   var defaultCustomFields = customFields || {};
-  
+
+  if(facility) {
+    defaultCustomFields['_facility'] = facility;
+  }
+
   var client = dgram.createSocket("udp4");
   
   process.on('exit', function() {