diff --git a/.github/workflows/browser_tests.yml b/.github/workflows/browser_tests.yml
index 69c4a075307..2ff007e6f8a 100644
--- a/.github/workflows/browser_tests.yml
+++ b/.github/workflows/browser_tests.yml
@@ -43,7 +43,6 @@ jobs:
 
       - name: Setup composer
         run: |
-            cp composer.json-dist composer.json
             composer require "laravel/dusk:^7.9" --no-update
 
       - name: Install dependencies
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index cb3884a1919..494a319fca8 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -40,7 +40,6 @@ jobs:
 
       - name: Setup composer
         run: |
-            cp composer.json-dist composer.json
             composer require "kolab/net_ldap3:~1.1.1" --no-update
 
       - name: Fix PHPUnit for PHP 8.2
diff --git a/INSTALL b/INSTALL
index d8a1b1cb97f..e4627665181 100644
--- a/INSTALL
+++ b/INSTALL
@@ -18,7 +18,7 @@ REQUIREMENTS
    - LDAP for LDAP addressbook support (optional)
    - GD, Imagick, XMLWriter (optional: thumbnails generation, QR-code)
 * PEAR and PEAR packages distributed with Roundcube or external.
-  See composer.json-dist for the list of required packages.
+  See composer.json for the list of required packages.
 * php.ini options:
    - memory_limit > 16MB
    - file_uploads enabled (for uploading attachments and import files)
@@ -40,7 +40,6 @@ INSTALLATION
   you have to install PHP and javascript dependencies.
   2.1. Install PHP dependencies using composer:
     - get composer from https://getcomposer.org/download/
-    - rename the composer.json-dist file into composer.json
     - if you want to use LDAP address books, enable the LDAP libraries in your
       composer.json file by moving the items from "suggest" to the "require"
       section (remove the explanation texts after the version!).
diff --git a/Makefile b/Makefile
index 861d590e883..244143eff44 100644
--- a/Makefile
+++ b/Makefile
@@ -18,7 +18,6 @@ all: clean complete dependent framework
 
 complete: roundcubemail-git
 	cp -RH roundcubemail-git roundcubemail-$(VERSION)
-	(cd roundcubemail-$(VERSION); cp composer.json-dist composer.json)
 	(cd roundcubemail-$(VERSION); php /tmp/composer.phar config platform.php $(PHP_VERSION))
 	(cd roundcubemail-$(VERSION); php /tmp/composer.phar require "kolab/net_ldap3:~1.1.1" --no-update --no-install)
 	(cd roundcubemail-$(VERSION); php /tmp/composer.phar config --unset suggest.kolab/net_ldap3)
diff --git a/UPGRADING b/UPGRADING
index cf3aec2fa82..b958cc6d603 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -52,7 +52,6 @@ it on a unix system, you need to do the following operations by hand:
    by running `php composer.phar update --no-dev`.
 4b. Install/update dependencies using composer:
    - get composer from https://getcomposer.org/download/
-   - rename the composer.json-dist file into composer.json
    - if you want to use LDAP address books, enable the LDAP libraries in your
      composer.json file by moving the items from "suggest" to the "require"
      section (remove the explanation texts after the version!).
diff --git a/bin/installto.sh b/bin/installto.sh
index fb515f324a0..f4a44bf78f5 100755
--- a/bin/installto.sh
+++ b/bin/installto.sh
@@ -77,7 +77,7 @@ if (strtolower($input) == 'y') {
         }
     }
 
-    foreach (['index.php','config/defaults.inc.php','composer.json-dist','jsdeps.json','CHANGELOG.md','README.md','UPGRADING','LICENSE','INSTALL'] as $file) {
+    foreach (['index.php','config/defaults.inc.php','composer.json','jsdeps.json','CHANGELOG.md','README.md','UPGRADING','LICENSE','INSTALL'] as $file) {
         $command = "rsync -a --out-format=%n " . INSTALL_PATH . "$file $target_dir/$file";
 
         if (file_exists(INSTALL_PATH . $file) && (system($command, $ret) === false || $ret > 0)) {
diff --git a/composer.json b/composer.json
index daa1c70ff1e..e6f599d3a27 100644
--- a/composer.json
+++ b/composer.json
@@ -29,6 +29,18 @@
         "kolab/net_ldap3": "~1.1.1 required for connecting to LDAP",
         "bjeavons/zxcvbn-php": "^1.0 required for Zxcvbn password strength driver"
     },
+    "autoload": {
+        "classmap":  [
+            "program/actions/",
+            "program/include/",
+            "program/lib/"
+        ]
+    },
+    "autoload-dev": {
+        "classmap": [
+            "tests/"
+        ]
+    },
     "config": {
         "allow-plugins": {
             "roundcube/plugin-installer": true
diff --git a/plugins/password/README b/plugins/password/README
index f4d21318c70..79412e79f5c 100644
--- a/plugins/password/README
+++ b/plugins/password/README
@@ -437,7 +437,7 @@
  -------------
 
  Driver to use the Zxcvbn library to check password strength. Requires zxcvbn-php library.
- The library is not distributed with Roundcube (see composer.json-dist).
+ The library is not distributed with Roundcube (see composer.json).
  Note: Required PHP's memory_limit >= 24M.
 
  Set $config['password_zxcvbn_min_score'] to define minimum acceptable password strength score.
diff --git a/program/include/iniset.php b/program/include/iniset.php
index a1e038420d3..506d3497c4b 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) {
-    die("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/README.md b/program/lib/Roundcube/README.md
index cce07febec1..966b10574a1 100644
--- a/program/lib/Roundcube/README.md
+++ b/program/lib/Roundcube/README.md
@@ -29,7 +29,7 @@ INSTALLATION
 ------------
 Copy all files of this directory to your project or install it in the default
 include_path directory of your webserver. Some classes of the framework require
-external libraries. See composer.json-dist for the list of required packages.
+external libraries. See composer.json for the list of required packages.
 
 
 USAGE
diff --git a/program/lib/Roundcube/bootstrap.php b/program/lib/Roundcube/bootstrap.php
index 2260cff6356..5f58a54bb29 100644
--- a/program/lib/Roundcube/bootstrap.php
+++ b/program/lib/Roundcube/bootstrap.php
@@ -90,19 +90,6 @@
 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 . $rcube_path);
-}
-
-// Register autoloader
-spl_autoload_register('rcube_autoload');
-
 // set PEAR error handling (will also load the PEAR main class)
 if (class_exists('PEAR')) {
     PEAR::setErrorHandling(PEAR_ERROR_CALLBACK, function($err) { rcube::raise_error($err, true); });
@@ -409,46 +396,3 @@ function version_parse($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/' . $classname;
-    }
-    else if (strpos($classname, 'html_') === 0 || $classname === 'html') {
-        $classname = 'Roundcube/html';
-    }
-    else if (strpos($classname, 'Mail_') === 0) {
-        $classname = 'Mail/' . substr($classname, 5);
-    }
-    else if (strpos($classname, 'Net_') === 0) {
-        $classname = 'Net/' . substr($classname, 4);
-    }
-    else if (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 8bbe6ae5b68..ac38bee4cce 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 573eca79fc7..886b22569a0 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -41,19 +41,6 @@
 
 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) {
-    die("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();