diff --git a/phpBB/phpbb/cache/driver/memory.php b/phpBB/phpbb/cache/driver/memory.php
index 0a4ea304ad..4ccd0607cd 100644
--- a/phpBB/phpbb/cache/driver/memory.php
+++ b/phpBB/phpbb/cache/driver/memory.php
@@ -45,6 +45,30 @@ abstract class memory extends \phpbb\cache\driver\base
 		}
 	}
 
+	/**
+	* {@inheritDoc}
+	*/
+	function purge()
+	{
+		unset($this->vars);
+		unset($this->sql_rowset);
+		unset($this->sql_row_pointer);
+
+		if (function_exists('opcache_reset'))
+		{
+			@opcache_reset();
+		}
+
+		$this->vars = [];
+		$this->sql_rowset = [];
+		$this->sql_row_pointer = [];
+
+		$this->is_modified = true;
+
+		// We save here to let the following cache hits succeed
+		$this->save();
+	}
+
 	/**
 	* {@inheritDoc}
 	*/
diff --git a/phpBB/phpbb/cache/driver/redis.php b/phpBB/phpbb/cache/driver/redis.php
index 6f103bf0f0..5a8332a15b 100644
--- a/phpBB/phpbb/cache/driver/redis.php
+++ b/phpBB/phpbb/cache/driver/redis.php
@@ -141,7 +141,7 @@ class redis extends \phpbb\cache\driver\memory
 	 */
 	protected function _delete(string $var): bool
 	{
-		if ($this->redis->delete($var) > 0)
+		if ($this->redis->del($var) > 0)
 		{
 			return true;
 		}