diff --git a/.github/build-packages.php b/.github/build-packages.php
index b67a699609..83f4b4336c 100644
--- a/.github/build-packages.php
+++ b/.github/build-packages.php
@@ -14,7 +14,7 @@ $packages = array();
 $flags = \PHP_VERSION_ID >= 50400 ? JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE : 0;
 
 foreach ($dirs as $k => $dir) {
-    if (!system("git diff --name-only $mergeBase -- $dir", $exitStatus)) {
+    if (!system("git diff --name-only \"$mergeBase\" -- $dir", $exitStatus)) {
         if ($exitStatus) {
             exit($exitStatus);
         }
diff --git a/appveyor.yml b/appveyor.yml
index 45373a9358..0d18c4bfe5 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -53,7 +53,7 @@ install:
     - php composer.phar self-update
     - copy /Y .composer\* %APPDATA%\Composer\
     - php composer.phar global require --no-progress --no-scripts --no-plugins symfony/flex dev-master
-    - php .github/build-packages.php "HEAD^" src\Symfony\Bridge\PhpUnit
+    - php .github/build-packages.php %APPVEYOR_REPO_COMMIT%^^ src\Symfony\Bridge\PhpUnit
     - IF %APPVEYOR_REPO_BRANCH%==master (SET COMPOSER_ROOT_VERSION=dev-master) ELSE (SET COMPOSER_ROOT_VERSION=%APPVEYOR_REPO_BRANCH%.x-dev)
     - php composer.phar config platform.php 5.5.9
     - php composer.phar update --no-progress --no-suggest --ansi