diff --git a/lib/block_io.php b/lib/block_io.php
index 98d9db2..c3919aa 100644
--- a/lib/block_io.php
+++ b/lib/block_io.php
@@ -128,7 +128,7 @@ private function _withdraw($name, $args = array())
 
 	 $response = $this->_request($name,$args);
 
-	 if ($response->status == 'success' && array_key_exists('reference_id', $response->data))
+	 if ($response->status == 'success' && property_exists($response->data, 'reference_id'))
 	 { // we have signatures to append
 	 
 	   // get our encryption key ready
@@ -189,7 +189,7 @@ private function _sweep($name, $args = array())
 	 
 	 $response = $this->_request($name,$args);
 
-	 if ($response->status == 'success' && array_key_exists('reference_id', $response->data))
+	 if ($response->status == 'success' && property_exists($response->data, 'reference_id'))
 	 { // we have signatures to append
 
 	   // grab inputs
@@ -1623,4 +1623,4 @@ function strToHex($string)
     return $hex;
 }
 
-?>
\ No newline at end of file
+?>