diff --git a/CImage.php b/CImage.php
index 94f745d..d641411 100644
--- a/CImage.php
+++ b/CImage.php
@@ -296,8 +296,10 @@ class CImage
         $this->saveFolder     = $dir;
         $this->cacheFileName  = $dir . '/' . $src;
 
+        /* Allow readonly cache
         is_writable($this->saveFolder)
             or $this->raiseError('Target directory is not writable.');
+        */
 
         // Sanitize filename
         $this->cacheFileName = preg_replace('/^a-zA-Z0-9\.-_/', '', $this->cacheFileName);
@@ -1462,6 +1464,9 @@ class CImage
             $this->setTarget($src, $base);
         }
 
+        is_writable($this->saveFolder)
+            or $this->raiseError('Target directory is not writable.');
+
         switch(strtolower($this->extension)) {
             
             case 'jpeg':
diff --git a/README.md b/README.md
index b0b95ac..59e06a5 100644
--- a/README.md
+++ b/README.md
@@ -133,6 +133,7 @@ Revision history
 
 v0.5.x (latest)
 
+* Cache-directory can now be readonly and serve all cached files, still failing when need to save files. #5
 * Cache now uses same file extension as original image #37. 
 * Can output image as json format using `json` #11.