diff --git a/core/phpunit.xml.dist b/core/phpunit.xml.dist
index 18e1f3b3e9..49a4aa3abe 100644
--- a/core/phpunit.xml.dist
+++ b/core/phpunit.xml.dist
@@ -64,11 +64,15 @@
     <whitelist>
       <directory>./includes</directory>
       <directory>./lib</directory>
+      <exclude>
+        <directory suffix=".api.php">./lib</directory>
+      </exclude>
       <!-- Extensions can have their own test directories, so exclude those. -->
       <directory>./modules</directory>
       <exclude>
         <directory>./modules/*/src/Tests</directory>
         <directory>./modules/*/tests</directory>
+        <directory suffix=".api.php">./modules</directory>
       </exclude>
       <directory>../modules</directory>
       <exclude>