diff --git a/phpBB/phpbb/cache/driver/apcu.php b/phpBB/phpbb/cache/driver/apcu.php
old mode 100644
new mode 100755
index 40192e4026..6a65e7155a
--- a/phpBB/phpbb/cache/driver/apcu.php
+++ b/phpBB/phpbb/cache/driver/apcu.php
@@ -25,7 +25,11 @@ class apcu extends \phpbb\cache\driver\memory
 	*/
 	function purge()
 	{
-		apcu_clear_cache();
+		/* use an iterator to selectively clear our cache entries without
+		   disturbing any other cache users
+		   (e.g. other phpBB boards hosted on this server) */
+		   apcu_delete(new \APCUIterator('#^' . $this->key_prefix . '#'));
+
 
 		parent::purge();
 	}
diff --git a/tests/cache/apcu_driver_test.php b/tests/cache/apcu_driver_test.php
old mode 100644
new mode 100755
index 9de1d82a15..2002fb66d8
--- a/tests/cache/apcu_driver_test.php
+++ b/tests/cache/apcu_driver_test.php
@@ -49,10 +49,27 @@ class phpbb_cache_apcu_driver_test extends phpbb_cache_common_test_case
 
 	protected function setUp()
 	{
+		global $phpbb_container, $phpbb_root_path;
+
 		parent::setUp();
 
+		$phpbb_container = new phpbb_mock_container_builder();
+		$phpbb_container->setParameter('core.cache_dir', $phpbb_root_path . 'cache/' . PHPBB_ENVIRONMENT . '/');
+
 		$this->driver = new \phpbb\cache\driver\apcu;
 
 		$this->driver->purge();
 	}
+
+		public function test_purge()
+	{
+		/* add a cache entry which does not match our key */
+		$foreign_key = 'test_' . $this->driver->key_prefix . 'test';
+		$this->assertSame(true, apcu_store($foreign_key, 0, 600));
+		$this->assertSame(true, apcu_exists($foreign_key));
+
+		parent::test_purge();
+
+		$this->assertSame(true, apcu_exists($foreign_key));
+	}
 }