diff --git a/change_log.txt b/change_log.txt
index a87d4383..8dc968b6 100644
--- a/change_log.txt
+++ b/change_log.txt
@@ -1,6 +1,9 @@
  ===== 3.1.22-dev ===== (xx.xx.2015)
  05.05.2015
- - bugfix code could be messed up when {tags} are used in multiple attributes https://github.com/smarty-php/smarty/issues/23
+ - optimization on cache update when main template is modified
+
+ 05.05.2015
+  - bugfix code could be messed up when {tags} are used in multiple attributes https://github.com/smarty-php/smarty/issues/23
  
  04.05.2015
   - bugfix Smarty_Resource::parseResourceName incompatible with Google AppEngine (https://github.com/smarty-php/smarty/issues/22)
diff --git a/libs/Smarty.class.php b/libs/Smarty.class.php
index bb1d658f..8c41f7ad 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/24';
+    const SMARTY_VERSION = '3.1.22-dev/25';
 
     /**
      * define variable scopes
diff --git a/libs/sysplugins/smarty_template_cached.php b/libs/sysplugins/smarty_template_cached.php
index 7824dc48..8721e2ca 100644
--- a/libs/sysplugins/smarty_template_cached.php
+++ b/libs/sysplugins/smarty_template_cached.php
@@ -138,6 +138,9 @@ class Smarty_Template_Cached
                 } else {
                     $cached->valid = true;
                 }
+                if ($cached->valid && $_template->source->timestamp > $cached->timestamp) {
+                    $cached->valid = false;
+                }
                 if ($cached->valid && $_template->caching == Smarty::CACHING_LIFETIME_CURRENT && $_template->cache_lifetime >= 0 && time() > ($cached->timestamp + $_template->cache_lifetime)) {
                     // lifetime expired
                     $cached->valid = false;