diff --git a/composer.json b/composer.json
index fc59e5e19d7..c8f3e84d698 100644
--- a/composer.json
+++ b/composer.json
@@ -34,6 +34,18 @@
             "url": "https://plugins.roundcube.net"
         }
     ],
+    "autoload": {
+        "classmap": [
+            "program/actions/",
+            "program/include/",
+            "program/lib/"
+        ]
+    },
+    "autoload-dev": {
+        "classmap": [
+            "tests/"
+        ]
+    },
     "config": {
         "allow-plugins": {
             "ergebnis/composer-normalize": true,
diff --git a/program/include/iniset.php b/program/include/iniset.php
index 10840321e86..af066d1644e 100644
--- a/program/include/iniset.php
+++ b/program/include/iniset.php
@@ -45,16 +45,6 @@
 // Show basic error message on fatal PHP error
 register_shutdown_function('rcmail_error_handler');
 
-// RC include folders MUST be included FIRST to avoid other
-// possible not compatible libraries (i.e PEAR) to be included
-// instead the ones provided by RC
-$include_path = INSTALL_PATH . 'program/lib' . \PATH_SEPARATOR;
-$include_path .= ini_get('include_path');
-
-if (set_include_path($include_path) === false) {
-    exit('Fatal error: ini_set/set_include_path does not work.');
-}
-
 // increase maximum execution time for php scripts
 // (does not work in safe mode)
 @set_time_limit(120);
@@ -75,32 +65,7 @@
 }
 
 // include Roundcube Framework
-require_once 'Roundcube/bootstrap.php';
-
-// register autoloader for rcmail app classes
-spl_autoload_register('rcmail_autoload');
-
-/**
- * PHP5 autoloader routine for dynamic class loading
- */
-function rcmail_autoload($classname)
-{
-    if (strpos($classname, 'rcmail') === 0) {
-        if (preg_match('/^rcmail_action_([^_]+)_(.*)$/', $classname, $matches)) {
-            $filepath = INSTALL_PATH . "program/actions/{$matches[1]}/{$matches[2]}.php";
-        }
-        else {
-            $filepath = INSTALL_PATH . "program/include/$classname.php";
-        }
-
-        if (is_readable($filepath)) {
-            include_once $filepath;
-            return true;
-        }
-    }
-
-    return false;
-}
+require_once __DIR__ . '/../lib/Roundcube/bootstrap.php';
 
 /**
  * Show a generic error message on fatal PHP error
diff --git a/program/lib/Roundcube/bootstrap.php b/program/lib/Roundcube/bootstrap.php
index 53e0e4d61ae..b6a55e14cd3 100644
--- a/program/lib/Roundcube/bootstrap.php
+++ b/program/lib/Roundcube/bootstrap.php
@@ -91,19 +91,6 @@
 mb_internal_encoding(RCUBE_CHARSET);
 mb_regex_encoding(RCUBE_CHARSET);
 
-// make sure the Roundcube lib directory is in the include_path
-$rcube_path = realpath(RCUBE_LIB_DIR . '..');
-$sep        = \PATH_SEPARATOR;
-$regexp     = "!(^|$sep)" . preg_quote($rcube_path, '!') . "($sep|\$)!";
-$path       = ini_get('include_path');
-
-if (!preg_match($regexp, $path)) {
-    set_include_path($path . \PATH_SEPARATOR . $rcube_path);
-}
-
-// Register autoloader
-spl_autoload_register('rcube_autoload');
-
 // set PEAR error handling (will also load the PEAR main class)
 if (class_exists('PEAR')) {
     PEAR::setErrorHandling(PEAR_ERROR_CALLBACK, static function ($err) { rcube::raise_error($err, true); });
@@ -403,46 +390,3 @@ function version_parse($version)
         $version
     );
 }
-
-/**
- * Use PHP5 autoload for dynamic class loading
- *
- * @param string $classname Class name
- *
- * @return bool True when the class file has been found
- *
- * @todo Make Zend, PEAR etc play with this
- * @todo Make our classes conform to a more straight forward CS.
- */
-function rcube_autoload($classname)
-{
-    if (strpos($classname, 'rcube') === 0) {
-        $classname = preg_replace('/^rcube_(cache|db|session|spellchecker)_/', '\\1/', $classname);
-        $classname = 'Roundcube/' . $classname;
-    }
-    elseif (strpos($classname, 'html_') === 0 || $classname === 'html') {
-        $classname = 'Roundcube/html';
-    }
-    elseif (strpos($classname, 'Mail_') === 0) {
-        $classname = 'Mail/' . substr($classname, 5);
-    }
-    elseif (strpos($classname, 'Net_') === 0) {
-        $classname = 'Net/' . substr($classname, 4);
-    }
-    elseif (strpos($classname, 'Auth_') === 0) {
-        $classname = 'Auth/' . substr($classname, 5);
-    }
-
-    // Translate PHP namespaces into directories,
-    // i.e. use \Sabre\VObject; $vcf = VObject\Reader::read(...)
-    //      -> Sabre/VObject/Reader.php
-    $classname = str_replace('\\', '/', $classname);
-
-    if ($fp = @fopen("$classname.php", 'r', true)) {
-        fclose($fp);
-        include_once "$classname.php";
-        return true;
-    }
-
-    return false;
-}
diff --git a/tests/Browser/bootstrap.php b/tests/Browser/bootstrap.php
index ea0cbbf68bd..d7a3c9959ad 100644
--- a/tests/Browser/bootstrap.php
+++ b/tests/Browser/bootstrap.php
@@ -34,16 +34,6 @@
 define('TESTS_USER', $rcmail->config->get('tests_username'));
 define('TESTS_PASS', $rcmail->config->get('tests_password'));
 
-require_once __DIR__ . '/Browser.php';
-require_once __DIR__ . '/TestCase.php';
-require_once __DIR__ . '/Components/App.php';
-require_once __DIR__ . '/Components/Dialog.php';
-require_once __DIR__ . '/Components/HtmlEditor.php';
-require_once __DIR__ . '/Components/Popupmenu.php';
-require_once __DIR__ . '/Components/RecipientInput.php';
-require_once __DIR__ . '/Components/Taskmenu.php';
-require_once __DIR__ . '/Components/Toolbarmenu.php';
-
 
 /**
  * Utilities for test environment setup
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index 3ffed0a0eb4..5bb993185cd 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -43,19 +43,6 @@
 
 rcmail::get_instance(0, 'test')->config->set('devel_mode', false);
 
-// Extend include path so some plugin test won't fail
-$include_path = ini_get('include_path') . \PATH_SEPARATOR . TESTS_DIR . '..';
-if (set_include_path($include_path) === false) {
-    exit('Fatal error: ini_set/set_include_path does not work.');
-}
-
-require_once TESTS_DIR . 'ActionTestCase.php';
-require_once TESTS_DIR . 'ExitException.php';
-require_once TESTS_DIR . 'OutputHtmlMock.php';
-require_once TESTS_DIR . 'OutputJsonMock.php';
-require_once TESTS_DIR . 'StderrMock.php';
-require_once TESTS_DIR . 'StorageMock.php';
-
 // Initialize database and environment
 ActionTestCase::init();