diff --git a/src/ExtensionInstaller.php b/src/ExtensionInstaller.php
index dff6d01..97de463 100644
--- a/src/ExtensionInstaller.php
+++ b/src/ExtensionInstaller.php
@@ -47,16 +47,17 @@ public function getInstallPath(PackageInterface $package)
 
     public function install(InstalledRepositoryInterface $repo, PackageInterface $package)
     {
-        // initialize Roundcube environment
         $this->setRoundcubemailInstallPath($repo);
-        if (!defined('INSTALL_PATH')) {
-            define('INSTALL_PATH', $this->getRoundcubemailInstallPath() . '/');
-        }
-        require_once INSTALL_PATH . 'program/include/iniset.php';
-
-        $this->rcubeVersionCheck($package);
 
         $postInstall = function () use ($package) {
+            // initialize Roundcube environment
+            if (!defined('INSTALL_PATH')) {
+                define('INSTALL_PATH', $this->getRoundcubemailInstallPath() . '/');
+            }
+            require_once INSTALL_PATH . 'program/include/iniset.php';
+
+            $this->rcubeVersionCheck($package);
+
             $config_file = $this->rcubeConfigFile();
             $package_name = $this->getPackageName($package);
             $package_dir = $this->getVendorDir() . \DIRECTORY_SEPARATOR . $package_name;
@@ -118,27 +119,28 @@ public function install(InstalledRepositoryInterface $repo, PackageInterface $pa
 
     public function update(InstalledRepositoryInterface $repo, PackageInterface $initial, PackageInterface $target)
     {
-        // initialize Roundcube environment
         $this->setRoundcubemailInstallPath($repo);
-        if (!defined('INSTALL_PATH')) {
-            define('INSTALL_PATH', $this->getRoundcubemailInstallPath() . '/');
-        }
-        require_once INSTALL_PATH . 'program/include/iniset.php';
 
-        $this->rcubeVersionCheck($target);
+        $postUpdate = function () use ($target) {
+            // initialize Roundcube environment
+            if (!defined('INSTALL_PATH')) {
+                define('INSTALL_PATH', $this->getRoundcubemailInstallPath() . '/');
+            }
+            require_once INSTALL_PATH . 'program/include/iniset.php';
 
-        $extra = $target->getExtra();
-        $fs = new Filesystem();
+            $this->rcubeVersionCheck($target);
 
-        // backup persistent files e.g. config.inc.php
-        $package_name = $this->getPackageName($initial);
-        $package_dir = $this->getVendorDir() . \DIRECTORY_SEPARATOR . $package_name;
-        $temp_dir = $package_dir . '-' . sprintf('%010d%010d', mt_rand(), mt_rand());
+            $extra = $target->getExtra();
+            $fs = new Filesystem();
+
+            // backup persistent files e.g. config.inc.php
+            $package_name = $this->getPackageName($initial);
+            $package_dir = $this->getVendorDir() . \DIRECTORY_SEPARATOR . $package_name;
+            $temp_dir = $package_dir . '-' . sprintf('%010d%010d', mt_rand(), mt_rand());
 
-        // make a backup of existing files (for restoring persistent files)
-        $fs->copy($package_dir, $temp_dir);
+            // make a backup of existing files (for restoring persistent files)
+            $fs->copy($package_dir, $temp_dir);
 
-        $postUpdate = function () use ($target, $extra, $fs, $temp_dir) {
             $package_name = $this->getPackageName($target);
             $package_dir = $this->getVendorDir() . \DIRECTORY_SEPARATOR . $package_name;
 
@@ -192,16 +194,17 @@ public function update(InstalledRepositoryInterface $repo, PackageInterface $ini
 
     public function uninstall(InstalledRepositoryInterface $repo, PackageInterface $package)
     {
-        // initialize Roundcube environment
         $this->setRoundcubemailInstallPath($repo);
-        if (!defined('INSTALL_PATH')) {
-            define('INSTALL_PATH', $this->getRoundcubemailInstallPath() . '/');
-        }
-        require_once INSTALL_PATH . 'program/include/iniset.php';
 
-        $config = $this->composer->getConfig()->get('roundcube');
+        $postUninstall = function () use ($package) {
+            // initialize Roundcube environment
+            if (!defined('INSTALL_PATH')) {
+                define('INSTALL_PATH', $this->getRoundcubemailInstallPath() . '/');
+            }
+            require_once INSTALL_PATH . 'program/include/iniset.php';
+
+            $config = $this->composer->getConfig()->get('roundcube');
 
-        $postUninstall = function () use ($package, $config) {
             // post-uninstall: deactivate package
             $package_name = $this->getPackageName($package);
             $package_dir = $this->getVendorDir() . \DIRECTORY_SEPARATOR . $package_name;