diff --git a/php_image_magician.php b/php_image_magician.php
index a582cbb..8a233ef 100755
--- a/php_image_magician.php
+++ b/php_image_magician.php
@@ -2513,7 +2513,7 @@ public function displayImage($fileType = 'jpg', $imageQuality="100")
             case 'jpg':
             case 'jpeg':
                 header('Content-type: image/jpeg');
-                imagejpeg($this->imageResized, '', $imageQuality);
+                imagejpeg($this->imageResized, NULL, $imageQuality);
                 break;
             case 'gif':
                 header('Content-type: image/gif');
@@ -2528,7 +2528,7 @@ public function displayImage($fileType = 'jpg', $imageQuality="100")
                 // *** Invert qualit setting as 0 is best, not 9
                 $invertScaleQuality = 9 - $scaleQuality;
 
-                imagepng($this->imageResized, '', $invertScaleQuality);
+                imagepng($this->imageResized, NULL, $invertScaleQuality);
                 break;
             case 'bmp':
                 echo 'bmp file format is not supported.';