diff --git a/lib/appenders/index.js b/lib/appenders/index.js
index db6a8b0..c31f470 100644
--- a/lib/appenders/index.js
+++ b/lib/appenders/index.js
@@ -39,7 +39,7 @@ const tryLoading = (modulePath, config) => {
 const loadAppenderModule = (type, config) => coreAppenders.get(type)
   || tryLoading(`./${type}`, config)
   || tryLoading(type, config)
-  || (require.main && tryLoading(path.join(path.dirname(require.main.filename), type), config))
+  || (require.main && require.main.filename && tryLoading(path.join(path.dirname(require.main.filename), type), config))
   || tryLoading(path.join(process.cwd(), type), config);
 
 const appendersLoading = new Set();