diff --git a/lib/phpunit/classes/util.php b/lib/phpunit/classes/util.php
index 8e44d8088cb..1fa42d4a46c 100644
--- a/lib/phpunit/classes/util.php
+++ b/lib/phpunit/classes/util.php
@@ -648,6 +648,14 @@ class phpunit_util {
         }
         get_fast_modinfo(0, 0, true);
 
+        // Reset other singletons.
+        if (class_exists('plugin_manager')) {
+            plugin_manager::reset_caches(true);
+        }
+        if (class_exists('available_update_checker')) {
+            available_update_checker::reset_caches(true);
+        }
+
         // purge dataroot directory
         self::reset_dataroot();
 
diff --git a/lib/pluginlib.php b/lib/pluginlib.php
index cb35acab04b..9191e7c36ac 100644
--- a/lib/pluginlib.php
+++ b/lib/pluginlib.php
@@ -86,6 +86,16 @@ class plugin_manager {
         return self::$singletoninstance;
     }
 
+    /**
+     * Reset any caches
+     * @param bool $phpunitreset
+     */
+    public static function reset_caches($phpunitreset = false) {
+        if ($phpunitreset) {
+            self::$singletoninstance = null;
+        }
+    }
+
     /**
      * Returns a tree of known plugins and information about them
      *
@@ -672,6 +682,16 @@ class available_update_checker {
         return self::$singletoninstance;
     }
 
+    /**
+     * Reset any caches
+     * @param bool $phpunitreset
+     */
+    public static function reset_caches($phpunitreset = false) {
+        if ($phpunitreset) {
+            self::$singletoninstance = null;
+        }
+    }
+
     /**
      * Returns the timestamp of the last execution of {@link fetch()}
      *