diff --git a/README.md b/README.md
index 11393d6..ea3c4a6 100644
--- a/README.md
+++ b/README.md
@@ -112,6 +112,8 @@ and consume 76 MB on a Surface Pro 3.
 The language server is fully operational while indexing and can respond to requests with the definitions already indexed.
 Follow-up requests will be almost instant because the index is kept in memory.
 
+Having XDebug enabled heavily impacts performance and can even crash the server if the `max_nesting_level` setting is too low.
+
 ## Versioning
 
 This project follows [semver](http://semver.org/) for the protocol communication and command line parameters,