diff --git a/README.md b/README.md
index 5ec9901..f4e66ae 100644
--- a/README.md
+++ b/README.md
@@ -22,7 +22,7 @@ module.exports = {
 };
 ```
 
-This extracts all SourceMaps from all files. That's not so performance-wise so you may only want to apply the loader to relevant files.
+This extracts SourceMaps from all js files (including node_modules). This is not very performant, so you may want to only apply the loader to relevant files.
 
 ## License