diff --git a/system/helpers/captcha_helper.php b/system/helpers/captcha_helper.php
index 36a5374..f4ed616 100644
--- a/system/helpers/captcha_helper.php
+++ b/system/helpers/captcha_helper.php
@@ -217,15 +217,15 @@
 		// -----------------------------------
 		$img_url = rtrim($img_url, '/').'/';
 
-		if (function_exists('ImageJPEG'))
+		if (function_exists('imagejpeg'))
 		{
 			$img_filename = $now.'.jpg';
-			ImageJPEG($im, $img_path.$img_filename);
+			imagejpeg($im, $img_path.$img_filename);
 		}
-		elseif (function_exists('ImagePNG'))
+		elseif (function_exists('imagepng'))
 		{
 			$img_filename = $now.'.png';
-			ImagePNG($im, $img_path.$img_filename);
+			imagepng($im, $img_path.$img_filename);
 		}
 		else
 		{
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index c37215d..2ed2275 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -137,7 +137,7 @@
       - Added *word_length* and *pool* options to allow customization of the generated word.
       - Added *colors* configuration to allow customization for the *background*, *border*, *text* and *grid* colors.
       - Added *filename* to the returned array elements.
-      - Using ImagePNG function, if ImageJPEG not exists.
+      - Updated to use `imagepng()` in case that `imagejpeg()` isn't available.
 
    -  :doc:`Text Helper <helpers/text_helper>` changes include: