diff --git a/CImage.php b/CImage.php
index 6aa0acc..1a1d790 100644
--- a/CImage.php
+++ b/CImage.php
@@ -2329,7 +2329,7 @@ private function createImageKeepTransparency($width, $height)
             ? imagecolortransparent($this->image)
             : -1;
 
-        if ($index != -1) {
+	    if ($index >= 0 && $index < imagecolorstotal($this->image)) {
 
             imagealphablending($img, true);
             $transparent = imagecolorsforindex($this->image, $index);