diff --git a/src/Composer/Repository/PlatformRepository.php b/src/Composer/Repository/PlatformRepository.php
index bb5509752..4db71f59c 100644
--- a/src/Composer/Repository/PlatformRepository.php
+++ b/src/Composer/Repository/PlatformRepository.php
@@ -122,7 +122,7 @@ class PlatformRepository extends ArrayRepository
         }
 
         // Check for xdebug in a restarted process
-        if ($prettyVersion = strval(getenv(XdebugHandler::ENV_VERSION))) {
+        if (!in_array('xdebug', $loadedExtensions, true) && ($prettyVersion = strval(getenv(XdebugHandler::ENV_VERSION)))) {
             $this->addExtension($versionParser, 'xdebug', $prettyVersion);
         }