diff --git a/tests/README.md b/tests/README.md
index e66acd2727ab..40755f1b65c6 100644
--- a/tests/README.md
+++ b/tests/README.md
@@ -19,7 +19,7 @@ If running under OS X or Linux, you can create a symbolic link to make running t
 	> ln -s ./vendor/bin/phpunit ./phpunit
 
 You also need to install [XDebug](https://xdebug.org/docs/install) in order
-for code coverage to be calculated successfully.
+for code coverage to be calculated successfully. After installing `XDebug`, you must add `xdebug.mode=coverage` in the **php.ini** file to enable code coverage.
 
 ## Setting Up