diff --git a/phpBB/adm/style/acp_ext_catalog.html b/phpBB/adm/style/acp_ext_catalog.html
index 345c32b067..326d6b8bc7 100644
--- a/phpBB/adm/style/acp_ext_catalog.html
+++ b/phpBB/adm/style/acp_ext_catalog.html
@@ -10,7 +10,7 @@
 <div class="errorbox">
 	{{ lang('EXTENSIONS_COMPOSER_NOT_WRITABLE') }}
 </div>
-{% endif %}I
+{% endif %}
 
 <fieldset class="quick quick-left">
 	<span class="small"><a href="https://www.phpbb.com/go/customise/extensions/3.1" target="_blank">{{ lang('BROWSE_EXTENSIONS_DATABASE') }}</a> &bull; <a href="javascript:phpbb.toggleDisplay('catalog_settings');">{{ lang('SETTINGS') }}</a></span>
diff --git a/phpBB/config/default/container/services_console.yml b/phpBB/config/default/container/services_console.yml
index a59fe3cd7e..94c7c61812 100644
--- a/phpBB/config/default/container/services_console.yml
+++ b/phpBB/config/default/container/services_console.yml
@@ -144,26 +144,27 @@ services:
     console.command.extension.install:
         class: phpbb\console\command\extension\install
         arguments:
-            - @user
-            - @ext.composer.manager
+            - '@user'
+            - '@ext.composer.manager'
+            - '@language'
         tags:
             - { name: console.command }
 
     console.command.extension.list_available:
         class: phpbb\console\command\extension\list_available
         arguments:
-            - @user
-            - @ext.composer.manager
-            - @language
+            - '@user'
+            - '@ext.composer.manager'
+            - '@language'
         tags:
             - { name: console.command }
 
     console.command.extension.manage:
         class: phpbb\console\command\extension\manage
         arguments:
-            - @user
-            - @ext.composer.manager
-            - @language
+            - '@user'
+            - '@ext.composer.manager'
+            - '@language'
         tags:
             - { name: console.command }
 
@@ -179,9 +180,9 @@ services:
     console.command.extension.remove:
         class: phpbb\console\command\extension\remove
         arguments:
-            - @user
-            - @ext.composer.manager
-            - @language
+            - '@user'
+            - '@ext.composer.manager'
+            - '@language'
         tags:
             - { name: console.command }
 
@@ -197,8 +198,9 @@ services:
     console.command.extension.update:
         class: phpbb\console\command\extension\update
         arguments:
-            - @user
-            - @ext.composer.manager
+            - '@user'
+            - '@ext.composer.manager'
+            - '@language'
         tags:
             - { name: console.command }
 
diff --git a/phpBB/config/default/container/services_extensions.yml b/phpBB/config/default/container/services_extensions.yml
index b97ae1fa9c..a28fd019d8 100644
--- a/phpBB/config/default/container/services_extensions.yml
+++ b/phpBB/config/default/container/services_extensions.yml
@@ -2,45 +2,45 @@ services:
     ext.manager:
         class: phpbb\extension\manager
         arguments:
-            - @service_container
-            - @dbal.conn
-            - @config
-            - @filesystem
-            - %tables.ext%
-            - %core.root_path%
-            - %core.php_ext%
-            - @cache
+            - '@service_container'
+            - '@dbal.conn'
+            - '@config'
+            - '@filesystem'
+            - '%tables.ext%'
+            - '%core.root_path%'
+            - '%core.php_ext%'
+            - '@cache'
 
     ext.composer.installer:
         class: phpbb\composer\installer
         arguments:
-            - %core.root_path%
-            - @config
+            - '%core.root_path%'
+            - '@config'
 
     ext.composer.manager:
         class: phpbb\composer\extension_manager
         arguments:
-            - @ext.composer.installer
-            - @cache.driver
-            - @ext.manager
-            - @filesystem
+            - '@ext.composer.installer'
+            - '@cache.driver'
+            - '@ext.manager'
+            - '@filesystem'
             - phpbb-extension
             - EXTENSIONS_
-            - %core.root_path%
-            - @config
+            - '%core.root_path%'
+            - '@config'
 
     style.composer.manager:
         class: phpbb\composer\manager
         arguments:
-            - @ext.composer.installer
-            - @cache.driver
+            - '@ext.composer.installer'
+            - '@cache.driver'
             - phpbb-style
             - STYLES_
 
     lang.composer.manager:
         class: phpbb\composer\manager
         arguments:
-            - @ext.composer.installer
-            - @cache.driver
+            - '@ext.composer.installer'
+            - '@cache.driver'
             - phpbb-language
             - LANGUAGES_
diff --git a/phpBB/language/en/acp/extensions.php b/phpBB/language/en/acp/extensions.php
index 8322be7753..a32676f31a 100644
--- a/phpBB/language/en/acp/extensions.php
+++ b/phpBB/language/en/acp/extensions.php
@@ -164,7 +164,7 @@ $lang = array_merge($lang, array(
 	'EXTENSIONS_REMOVED'			=> 'Extensions successfully removed.',
 	'EXTENSIONS_UPDATED'			=> 'Extensions successfully updated.',
 
-	'EXTENSIONS_COMPOSER_NOT_WRITABLE'	=> 'TODO: some required files / directory are not writable => disable ',
+	'EXTENSIONS_COMPOSER_NOT_WRITABLE'	=> 'In order to use the catalog, the following files and directories must be writable: ext/ vendor-ext/ composer-ext.json and composer-ext.json.lock',
 
 	'STABILITY_STABLE'	=> 'stable',
 	'STABILITY_RC'		=> 'RC',
diff --git a/phpBB/phpbb/composer/installer.php b/phpBB/phpbb/composer/installer.php
index 730d708d10..3605af135b 100644
--- a/phpBB/phpbb/composer/installer.php
+++ b/phpBB/phpbb/composer/installer.php
@@ -20,10 +20,10 @@ use Composer\IO\NullIO;
 use Composer\Json\JsonFile;
 use Composer\Package\BasePackage;
 use Composer\Package\CompletePackage;
-use Composer\Package\LinkConstraint\LinkConstraintInterface;
 use Composer\Package\PackageInterface;
 use Composer\Repository\ComposerRepository;
 use Composer\Repository\RepositoryInterface;
+use Composer\Semver\Constraint\ConstraintInterface;
 use Composer\Util\RemoteFilesystem;
 use phpbb\config\config;
 use phpbb\exception\runtime_exception;
@@ -85,7 +85,7 @@ class installer
 		{
 			$repositories        = json_decode($config['exts_composer_repositories'], true);
 
-			if (!is_array($repositories) && !empty($repositories))
+			if (is_array($repositories) && !empty($repositories))
 			{
 				$this->repositories = (array) $repositories;
 			}
@@ -296,7 +296,7 @@ class installer
 			$io = new NullIO();
 			$composer = Factory::create($io, $this->get_composer_ext_json_filename(), false);
 
-			/** @var LinkConstraintInterface $core_constraint */
+			/** @var ConstraintInterface $core_constraint */
 			$core_constraint = $composer->getPackage()->getRequires()['phpbb/phpbb']->getConstraint();
 			$core_stability = $composer->getPackage()->getMinimumStability();
 
@@ -430,14 +430,14 @@ class installer
 	 * Updates $compatible_packages with the versions of $versions compatibles with the $core_constraint
 	 *
 	 * @param array						$compatible_packages	List of compatibles versions
-	 * @param LinkConstraintInterface	$core_constraint		Constraint against the phpBB version
+	 * @param ConstraintInterface	$core_constraint		Constraint against the phpBB version
 	 * @param string $core_stability Core stability
 	 * @param string					$package_name			Considered package
 	 * @param array						$versions				List of available versions
 	 *
 	 * @return array
 	 */
-	private function get_compatible_versions(array $compatible_packages, LinkConstraintInterface $core_constraint, $core_stability, $package_name, array $versions)
+	private function get_compatible_versions(array $compatible_packages, ConstraintInterface $core_constraint, $core_stability, $package_name, array $versions)
 	{
 		$core_stability_value = BasePackage::$stabilities[$core_stability];
 		//VersionParser::parseStability($version['version'])
@@ -451,7 +451,7 @@ class installer
 
 			if (array_key_exists('phpbb/phpbb', $version->getRequires()))
 			{
-				/** @var LinkConstraintInterface $package_constraint */
+				/** @var ConstraintInterface $package_constraint */
 				$package_constraint = $version->getRequires()['phpbb/phpbb']->getConstraint();
 
 				if (!$package_constraint->matches($core_constraint))
diff --git a/phpBB/phpbb/db/migration/data/v320/extensions_composer.php b/phpBB/phpbb/db/migration/data/v320/extensions_composer.php
index 8b7065d335..957d141683 100644
--- a/phpBB/phpbb/db/migration/data/v320/extensions_composer.php
+++ b/phpBB/phpbb/db/migration/data/v320/extensions_composer.php
@@ -18,8 +18,10 @@ class extensions_composer extends \phpbb\db\migration\migration
 	public function update_data()
 	{
 		return array(
-			array('config.add', array('exts_composer_repositories', json_encode([], JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES))),
-			array('config.add', array('exts_composer_packagist', true)),
+			array('config.add', array('exts_composer_repositories', json_encode([
+				'https://www.phpbb.com/customise/db/composer/',
+			], JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES))),
+			array('config.add', array('exts_composer_packagist', false)),
 			array('config.add', array('exts_composer_json_file', 'composer-ext.json')),
 			array('config.add', array('exts_composer_vendor_dir', 'vendor-ext/')),
 			array('config.add', array('exts_composer_enable_on_install', false)),