diff --git a/lib/appenders/index.js b/lib/appenders/index.js
index d7408b8..cd7ad96 100644
--- a/lib/appenders/index.js
+++ b/lib/appenders/index.js
@@ -34,7 +34,7 @@ const tryLoading = (modulePath, config) => {
 const loadAppenderModule = (type, config) => coreAppenders.get(type) ||
   tryLoading(`./${type}`, config) ||
   tryLoading(type, config) ||
-  tryLoading(path.join(path.dirname(require.main.filename), type), config) ||
+  (require.main && tryLoading(path.join(path.dirname(require.main.filename), type), config)) ||
   tryLoading(path.join(process.cwd(), type), config);
 
 const createAppender = (name, config) => {