diff --git a/phpBB/phpbb/captcha/plugins/legacy_wrapper.php b/phpBB/phpbb/captcha/plugins/legacy_wrapper.php
index e57abbb967..5f2c701e07 100644
--- a/phpBB/phpbb/captcha/plugins/legacy_wrapper.php
+++ b/phpBB/phpbb/captcha/plugins/legacy_wrapper.php
@@ -74,6 +74,19 @@ class legacy_wrapper implements plugin_interface
 		}
 	}
 
+	/**
+	 * {@inheritDoc}
+	 */
+	public function get_hidden_fields(): array
+	{
+		if (method_exists($this->legacy_captcha, 'get_hidden_fields'))
+		{
+			return $this->legacy_captcha->get_hidden_fields();
+		}
+
+		return [];
+	}
+
 	/**
 	 * {@inheritDoc}
 	 */
diff --git a/phpBB/phpbb/captcha/plugins/plugin_interface.php b/phpBB/phpbb/captcha/plugins/plugin_interface.php
index 41e825fad3..9286c4867e 100644
--- a/phpBB/phpbb/captcha/plugins/plugin_interface.php
+++ b/phpBB/phpbb/captcha/plugins/plugin_interface.php
@@ -52,6 +52,13 @@ interface plugin_interface
 	 */
 	public function init(int $type): void;
 
+	/**
+	 * Get hidden form fields for this captcha plugin
+	 *
+	 * @return array Hidden form fields
+	 */
+	public function get_hidden_fields(): array;
+
 	/**
 	 * Validate the captcha with the given request data
 	 *