diff --git a/index.ts b/index.ts
index 04b6881d4..b861e284c 100644
--- a/index.ts
+++ b/index.ts
@@ -250,13 +250,13 @@ function ensureTypeScriptInstance(loaderOptions: LoaderOptions, loader: any): {
         configParseResult = (<TSCompatibleCompiler><any>compiler).parseJsonConfigFileContent(
             configFile.config,
             compiler.sys,
-            path.dirname(configFilePath)
+            path.dirname(configFilePath || '')
         );
     } else {
         configParseResult = (<TSCompatibleCompiler><any>compiler).parseConfigFile(
             configFile.config,
             compiler.sys,
-            path.dirname(configFilePath)
+            path.dirname(configFilePath || '')
         );
     }