diff --git a/lib/behat/classes/util.php b/lib/behat/classes/util.php
index 8237f6013ce..1b15f106ab8 100644
--- a/lib/behat/classes/util.php
+++ b/lib/behat/classes/util.php
@@ -435,6 +435,9 @@ class behat_util extends testing_util {
         // Inform data generator.
         self::get_data_generator()->reset();
 
+        // Reset the task manager.
+        \core\task\manager::reset_state();
+
         // Initialise $CFG with default values. This is needed for behat cli process, so we don't have modified
         // $CFG values from the old run. @see set_config.
         self::remove_added_config();
diff --git a/lib/classes/task/manager.php b/lib/classes/task/manager.php
index 4b56f81438f..d839eedac75 100644
--- a/lib/classes/task/manager.php
+++ b/lib/classes/task/manager.php
@@ -63,17 +63,26 @@ class manager {
     /**
      * @var array A cached queue of adhoc tasks
      */
-    public static $miniqueue;
+    protected static array $miniqueue = [];
 
     /**
      * @var int The last recorded number of unique adhoc tasks.
      */
-    public static $numtasks;
+    protected static int $numtasks = 0;
 
     /**
-     * @var string Used to determine if the adhoc task queue is distributing or filling capacity.
+     * @var null|int Used to determine if the adhoc task queue is distributing or filling capacity.
      */
-    public static $mode;
+    protected static ?int $mode = null;
+
+    /**
+     * Reset the state of the task manager.
+     */
+    public static function reset_state(): void {
+        self::$miniqueue = [];
+        self::$numtasks = 0;
+        self::$mode = null;
+    }
 
     /**
      * Given a component name, will load the list of tasks in the db/tasks.php file for that component.
diff --git a/lib/upgrade.txt b/lib/upgrade.txt
index c3d5fccdd1d..abbbf7d2aec 100644
--- a/lib/upgrade.txt
+++ b/lib/upgrade.txt
@@ -57,6 +57,10 @@ information provided here is intended especially for developers.
   is applied.
 * The Horde library has been removed from core. It was only used by the tool_messageinbound. Now tool_messageinbound
   uses the new RoundCube library.
+* Visibility of internal properties of the \core\task\manager have been changed from public to protected. These should not have been accessible.
+  - $miniqueue
+  - $numtasks
+  - $mode
 
 === 4.3 ===