diff --git a/core/Cache/PersistentCache.php b/core/Cache/PersistentCache.php
index cd695bde2d5011b79b31a36a17dbefa300faf4bf..2596b950a590f8a3b24b76a854f0e84da849db2a 100644
--- a/core/Cache/PersistentCache.php
+++ b/core/Cache/PersistentCache.php
@@ -96,7 +96,7 @@ class PersistentCache
 
     public static function _reset()
     {
-        self::$content = null;
+        self::$content = array();
     }
 
     /**
@@ -106,6 +106,9 @@ class PersistentCache
     {
         if (is_null(self::$storage)) {
             self::$storage = new CacheFile('tracker', 43200);
+            self::$storage->addOnDeleteCallback(function () {
+                PersistentCache::_reset();
+            });
         }
 
         return self::$storage;
diff --git a/core/CacheFile.php b/core/CacheFile.php
index 94ad253020ad40b83244a227cf99e10c9cabbafb..7a1c824ff8977eb8a4de2be58b1c06a0b7a22d07 100644
--- a/core/CacheFile.php
+++ b/core/CacheFile.php
@@ -36,6 +36,11 @@ class CacheFile
      */
     const MINIMUM_TTL = 60;
 
+    /**
+     * @var \Callable[]
+     */
+    private static $onDeleteCallback = array();
+
     /**
      * @param string $directory directory to use
      * @param int $timeToLiveInSeconds TTL
@@ -182,6 +187,11 @@ class CacheFile
         return false;
     }
 
+    public function addOnDeleteCallback($onDeleteCallback)
+    {
+        self::$onDeleteCallback[] = $onDeleteCallback;
+    }
+
     /**
      * A function to delete all cache entries in the directory
      */
@@ -193,6 +203,12 @@ class CacheFile
         };
 
         Filesystem::unlinkRecursive($this->cachePath, $deleteRootToo = false, $beforeUnlink);
+
+        if (!empty(self::$onDeleteCallback)) {
+            foreach (self::$onDeleteCallback as $callback) {
+                $callback();
+            }
+        }
     }
 
     public function opCacheInvalidate($filepath)
diff --git a/tests/PHPUnit/Fixture.php b/tests/PHPUnit/Fixture.php
index cb5fac1035a97ccd2940fd0e5ff79c3568137d9b..22b09767a3c78c87a916782cd0d4cac1cb3a1a6c 100644
--- a/tests/PHPUnit/Fixture.php
+++ b/tests/PHPUnit/Fixture.php
@@ -179,7 +179,6 @@ class Fixture extends PHPUnit_Framework_Assert
         Piwik::setUserHasSuperUserAccess();
 
         Cache::deleteTrackerCache();
-        \Piwik\Cache\PersistentCache::_reset();
 
         static::loadAllPlugins($this->getTestEnvironment(), $this->testCaseClass);