diff --git a/setup/src/Magento/Setup/Module/Di/Code/Reader/ClassesScanner.php b/setup/src/Magento/Setup/Module/Di/Code/Reader/ClassesScanner.php
index 38848ef13caafd2d9c72e32bae2b005de318de84..9e7a60b642b302e49d4f8b4a08d0585940758d17 100644
--- a/setup/src/Magento/Setup/Module/Di/Code/Reader/ClassesScanner.php
+++ b/setup/src/Magento/Setup/Module/Di/Code/Reader/ClassesScanner.php
@@ -88,7 +88,7 @@ class ClassesScanner implements ClassesScannerInterface
             $patterns = (array)$patterns;
         }
         foreach ($patterns as $pattern) {
-            if (preg_match($pattern, $fileItem->getRealPath())) {
+            if (preg_match($pattern, str_replace('\\', '/', $fileItem->getRealPath()))) {
                 return true;
             }
         }