diff --git a/wp-common b/wp-common
index c4fb20b..ec68d31 160000
--- a/wp-common
+++ b/wp-common
@@ -1 +1 @@
-Subproject commit c4fb20b46ce51d157a0ccd0d60f73273d4547fef
+Subproject commit ec68d31126706b193d1226819c6886fa6d2312a2
diff --git a/wp-ffpc-backend.php b/wp-ffpc-backend.php
index c684e66..c323116 100644
--- a/wp-ffpc-backend.php
+++ b/wp-ffpc-backend.php
@@ -115,7 +115,7 @@ if (!class_exists('WP_FFPC_Backend')) {
 		 */
 		public function key ( &$prefix ) {
 			/* data is string only with content, meta is not used in nginx */
-			$key = str_replace ( array_keys( $this->urimap ), $this->urimap, $this->options['key'] );
+			$key = $prefix . str_replace ( array_keys( $this->urimap ), $this->urimap, $this->options['key'] );
 			$this->log (  __translate__('original key configuration: ', $this->plugin_constant ) . $this->options['key'] );
 			$this->log (  __translate__('setting key to: ', $this->plugin_constant ) . $key );
 
@@ -782,4 +782,4 @@ if (!class_exists('WP_FFPC_Backend')) {
 
 }
 
-?>
\ No newline at end of file
+?>