diff --git a/change_log.txt b/change_log.txt
index 87d0e8d1..0e56d0ab 100644
--- a/change_log.txt
+++ b/change_log.txt
@@ -1,6 +1,7 @@
  ===== 3.1.22-dev ===== (xx.xx.2015)
  06.05.2015
   - bugfix in 3.1.22-dev cache resource must not be loaded for subtemplates
+  - bugfix/improvement in 3.1.22-dev cache locking did not work as expected
   
  05.05.2015
   - optimization on cache update when main template is modified
diff --git a/libs/Smarty.class.php b/libs/Smarty.class.php
index 35db7837..6a807eb0 100644
--- a/libs/Smarty.class.php
+++ b/libs/Smarty.class.php
@@ -111,7 +111,7 @@ class Smarty extends Smarty_Internal_TemplateBase
     /**
      * smarty version
      */
-    const SMARTY_VERSION = '3.1.22-dev/27';
+    const SMARTY_VERSION = '3.1.22-dev/28';
 
     /**
      * define variable scopes
diff --git a/libs/sysplugins/smarty_internal_cacheresource_file.php b/libs/sysplugins/smarty_internal_cacheresource_file.php
index 72ed7692..de794517 100644
--- a/libs/sysplugins/smarty_internal_cacheresource_file.php
+++ b/libs/sysplugins/smarty_internal_cacheresource_file.php
@@ -61,7 +61,7 @@ class Smarty_Internal_CacheResource_File extends Smarty_CacheResource
             $cached->lock_id = $_lock_dir . sha1($_cache_id . $_compile_id . $_template->source->uid) . '.lock';
         }
         $cached->filepath = $_cache_dir . $_cache_id . $_compile_id . $_filepath . '.' . basename($_source_file_path) . '.php';
-        $cached->exists = is_file($cached->filepath);
+        $cached->timestamp = $cached->exists = is_file($cached->filepath);
         if ($cached->exists) {
             $cached->timestamp = filemtime($cached->filepath);
         }
@@ -113,7 +113,7 @@ class Smarty_Internal_CacheResource_File extends Smarty_CacheResource
         $obj = new Smarty_Internal_Write_File();
         if ($obj->writeFile($_template->cached->filepath, $content, $_template->smarty) === true) {
             $cached = $_template->cached;
-            $cached->timestamp = $cached->exists = is_file( $cached->filepath);
+            $cached->timestamp = $cached->exists = is_file($cached->filepath);
             if ($cached->exists) {
                 $cached->timestamp = filemtime($cached->filepath);
                 return true;
diff --git a/libs/sysplugins/smarty_internal_template.php b/libs/sysplugins/smarty_internal_template.php
index 454828bd..55b3214f 100644
--- a/libs/sysplugins/smarty_internal_template.php
+++ b/libs/sysplugins/smarty_internal_template.php
@@ -603,7 +603,7 @@ class Smarty_Internal_Template extends Smarty_Internal_TemplateBase
                     } else {
                         // file and php types can be checked without loading the respective resource handlers
                         $mtime = is_file($_file_to_check[0]) ? @filemtime($_file_to_check[0]) : false;
-                     }
+                    }
                 } elseif ($_file_to_check[2] == 'string') {
                     continue;
                 } else {
diff --git a/libs/sysplugins/smarty_internal_templatebase.php b/libs/sysplugins/smarty_internal_templatebase.php
index f0c3fd40..b629aedc 100644
--- a/libs/sysplugins/smarty_internal_templatebase.php
+++ b/libs/sysplugins/smarty_internal_templatebase.php
@@ -56,17 +56,18 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
     public function isCached($template = null, $cache_id = null, $compile_id = null, $parent = null)
     {
         if ($template === null && $this instanceof $this->template_class) {
-            return $this->cached->valid;
-        }
-        if (!($template instanceof $this->template_class)) {
-            if ($parent === null) {
-                $parent = $this;
+            $template = $this;
+        } else {
+            if (!($template instanceof $this->template_class)) {
+                if ($parent === null) {
+                    $parent = $this;
+                }
+                $smarty = isset($this->smarty) ? $this->smarty : $this;
+                $template = $smarty->createTemplate($template, $cache_id, $compile_id, $parent, false);
             }
-            $smarty = isset($this->smarty) ? $this->smarty : $this;
-            $template = $smarty->createTemplate($template, $cache_id, $compile_id, $parent, false);
         }
         // return cache status of template
-        return $template->cached->valid;
+        return $template->cached->isCached($template);
     }
 
     /**
@@ -120,7 +121,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      * @param  boolean  $cacheable  if true (default) this fuction is cachable
      * @param  array    $cache_attr caching attributes if any
      *
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      * @throws SmartyException              when the plugin tag is invalid
      */
     public function registerPlugin($type, $tag, $callback, $cacheable = true, $cache_attr = null)
@@ -143,7 +145,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      * @param  string $type of plugin
      * @param  string $tag  name of plugin
      *
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      */
     public function unregisterPlugin($type, $tag)
     {
@@ -159,9 +162,11 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      * Registers a resource to fetch a template
      *
      * @param  string                $type     name of resource type
-     * @param  Smarty_Resource|array $callback or instance of Smarty_Resource, or array of callbacks to handle resource (deprecated)
+     * @param  Smarty_Resource|array $callback or instance of Smarty_Resource, or array of callbacks to handle resource
+     *                                         (deprecated)
      *
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      */
     public function registerResource($type, $callback)
     {
@@ -176,7 +181,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      *
      * @param  string $type name of resource type
      *
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      */
     public function unregisterResource($type)
     {
@@ -194,7 +200,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      * @param  string               $type     name of cache resource type
      * @param  Smarty_CacheResource $callback instance of Smarty_CacheResource to handle output caching
      *
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      */
     public function registerCacheResource($type, Smarty_CacheResource $callback)
     {
@@ -209,7 +216,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      *
      * @param  string $type name of cache resource type
      *
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      */
     public function unregisterCacheResource($type)
     {
@@ -231,7 +239,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      * @param  array   $block_methods list of block-methods
      *
      * @throws SmartyException
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      */
     public function registerObject($object_name, $object_impl, $allowed = array(), $smarty_args = true, $block_methods = array())
     {
@@ -285,7 +294,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      *
      * @param  string $name object name
      *
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      */
     public function unregisterObject($name)
     {
@@ -304,7 +314,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      * @param  string $class_impl the referenced PHP class to register
      *
      * @throws SmartyException
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      */
     public function registerClass($class_name, $class_impl)
     {
@@ -324,7 +335,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      *
      * @param  callable $callback class/method name
      *
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      * @throws SmartyException              if $callback is not callable
      */
     public function registerDefaultPluginHandler($callback)
@@ -344,7 +356,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      *
      * @param  callable $callback class/method name
      *
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      * @throws SmartyException              if $callback is not callable
      */
     public function registerDefaultTemplateHandler($callback)
@@ -358,7 +371,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      *
      * @param  callable $callback class/method name
      *
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      * @throws SmartyException              if $callback is not callable
      */
     public function registerDefaultConfigHandler($callback)
@@ -373,7 +387,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      * @param  string   $type filter type
      * @param  callback $callback
      *
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      */
     public function registerFilter($type, $callback)
     {
@@ -389,7 +404,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      * @param  string   $type filter type
      * @param  callback $callback
      *
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      */
     public function unregisterFilter($type, $callback)
     {
@@ -453,7 +469,8 @@ abstract class Smarty_Internal_TemplateBase extends Smarty_Internal_Data
      * @param  string $type filter type
      * @param  string $name filter name
      *
-     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or Smarty_Internal_Template) instance for chaining
+     * @return Smarty_Internal_Templatebase current Smarty_Internal_Templatebase (or Smarty or
+     *                                      Smarty_Internal_Template) instance for chaining
      */
     public function unloadFilter($type, $name)
     {
diff --git a/libs/sysplugins/smarty_template_cached.php b/libs/sysplugins/smarty_template_cached.php
index 9f35295c..ae8a329a 100644
--- a/libs/sysplugins/smarty_template_cached.php
+++ b/libs/sysplugins/smarty_template_cached.php
@@ -129,10 +129,17 @@ class Smarty_Template_Cached
         return $cached;
     }
 
-
+    /**
+     * Check if cache is valid, lock cache if required
+     *
+     * @param \Smarty_Internal_Template $_template
+     * @param bool                      $lock keep cache locked
+     *
+     * @return bool flag true if cache is valid
+     */
     public function isCached(Smarty_Internal_Template $_template, $lock = false)
     {
-        if ($this->valid  !== null) {
+        if ($this->valid !== null) {
             return $this->valid;
         }
         while (true) {
@@ -175,7 +182,7 @@ class Smarty_Template_Cached
                 if ($_template->smarty->cache_locking && !$lock) {
                     $this->handler->releaseLock($_template->smarty, $this);
                 }
-                    return $this->valid;
+                return $this->valid;
             }
             if ($this->valid && $_template->caching === Smarty::CACHING_LIFETIME_SAVED && $_template->properties['cache_lifetime'] >= 0 && (time() > ($_template->cached->timestamp + $_template->properties['cache_lifetime']))) {
                 $this->valid = false;