diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 6cc6a2b..333d408 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -21,7 +21,7 @@ on:
 jobs:
     # START Basic Checks Job (EPV, code sniffer, images check, etc.)
     basic-checks:
-        runs-on: ubuntu-20.04
+        runs-on: ubuntu-22.04
         strategy:
             matrix:
                 include:
@@ -33,14 +33,14 @@ jobs:
 
         steps:
             - name: Checkout phpBB
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
               with:
                   repository: phpbb/phpbb
                   ref: ${{ env.PHPBB_BRANCH }}
                   path: phpBB3
 
             - name: Checkout extension
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
               with:
                   path: phpBB3/phpBB/ext/${{ env.EXTNAME }}
 
@@ -89,7 +89,7 @@ jobs:
 
     # START MySQL and MariaDB Job
     mysql-tests:
-        runs-on: ubuntu-20.04
+        runs-on: ubuntu-22.04
         strategy:
             matrix:
                 include:
@@ -127,6 +127,8 @@ jobs:
                       db: "mysql:5.7"
                     - php: '8.3'
                       db: "mysql:5.7"
+                    - php: '8.4'
+                      db: "mysql:5.7"
 
         name: PHP ${{ matrix.php }} - ${{ matrix.db_alias != '' && matrix.db_alias || matrix.db }}
 
@@ -156,14 +158,14 @@ jobs:
 
         steps:
             - name: Checkout phpBB
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
               with:
                   repository: phpbb/phpbb
                   ref: ${{ env.PHPBB_BRANCH }}
                   path: phpBB3
 
             - name: Checkout extension
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
               with:
                   path: phpBB3/phpBB/ext/${{ env.EXTNAME }}
 
@@ -240,7 +242,7 @@ jobs:
 
     # START PostgreSQL Job
     postgres-tests:
-        runs-on: ubuntu-20.04
+        runs-on: ubuntu-22.04
         strategy:
             matrix:
                 include:
@@ -270,6 +272,8 @@ jobs:
                       db: "postgres:14"
                     - php: '8.3'
                       db: "postgres:14"
+                    - php: '8.4'
+                      db: "postgres:14"
 
         name: PHP ${{ matrix.php }} - ${{ matrix.db }}
 
@@ -301,14 +305,14 @@ jobs:
 
         steps:
             - name: Checkout phpBB
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
               with:
                   repository: phpbb/phpbb
                   ref: ${{ env.PHPBB_BRANCH }}
                   path: phpBB3
 
             - name: Checkout extension
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
               with:
                   path: phpBB3/phpBB/ext/${{ env.EXTNAME }}
 
@@ -354,7 +358,7 @@ jobs:
 
     # START Other Tests Job (SQLite 3 and mssql)
     other-tests:
-        runs-on: ubuntu-20.04
+        runs-on: ubuntu-22.04
         strategy:
             matrix:
                 include:
@@ -396,14 +400,14 @@ jobs:
 
         steps:
             - name: Checkout phpBB
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
               with:
                   repository: phpbb/phpbb
                   ref: ${{ env.PHPBB_BRANCH }}
                   path: phpBB3
 
             - name: Checkout extension
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
               with:
                   path: phpBB3/phpBB/ext/${{ env.EXTNAME }}
 
diff --git a/composer.json b/composer.json
index 7013feb..ad25952 100644
--- a/composer.json
+++ b/composer.json
@@ -27,7 +27,7 @@
 	"extra": {
 		"display-name": "phpBB Topic Prefixes",
 		"soft-require": {
-			"phpbb/phpbb": ">=3.2.0"
+			"phpbb/phpbb": ">=3.2.0,<4.0.0@dev"
 		},
 		"version-check": {
 			"host": "www.phpbb.com",
diff --git a/ext.php b/ext.php
index a82ff90..955cff4 100644
--- a/ext.php
+++ b/ext.php
@@ -31,6 +31,8 @@ class ext extends \phpbb\extension\base
 	 */
 	public function is_enableable()
 	{
-		return phpbb_version_compare(PHPBB_VERSION, '3.2.0', '>=') && phpbb_version_compare(PHP_VERSION, '5.4', '>=');
+		return phpbb_version_compare(PHPBB_VERSION, '3.2.0', '>=')
+			&& phpbb_version_compare(PHPBB_VERSION, '4.0.0-dev', '<')
+			&& PHP_VERSION_ID >= 50400;
 	}
 }