diff --git a/phpBB/docs/CHANGELOG.html b/phpBB/docs/CHANGELOG.html
index 11b348949d..091fcc0d09 100644
--- a/phpBB/docs/CHANGELOG.html
+++ b/phpBB/docs/CHANGELOG.html
@@ -97,6 +97,7 @@
 		<li>[Fix] Update correct theme for cached styles in style.php (Bug #25805)</li>
 		<li>[Fix] Also add PHPBB_INSTALLED check to download/file.php for inline avatar delivery</li>
 		<li>[Fix] Unable to login to some jabber server, reverted previous change (Bug #25095)</li>
+		<li>[Fix] Do not return BMP as valid image type for GD image manipulation (Bug #25925)</li>
 	</ul>
 
 	<a name="v300"></a><h3>1.ii. Changes since 3.0.0</h3>
diff --git a/phpBB/includes/functions_posting.php b/phpBB/includes/functions_posting.php
index 2f12732e8b..709516a2b0 100644
--- a/phpBB/includes/functions_posting.php
+++ b/phpBB/includes/functions_posting.php
@@ -524,6 +524,8 @@ function get_supported_image_types($type = false)
 
 		if ($type !== false)
 		{
+			// Type is one of the IMAGETYPE constants - it is fetched from getimagesize()
+			// We do not use the constants here, because some were not available in PHP 4.3.x
 			switch ($type)
 			{
 				// GIF
@@ -545,8 +547,7 @@ function get_supported_image_types($type = false)
 					$new_type = ($format & IMG_PNG) ? IMG_PNG : false;
 				break;
 
-				// BMP, WBMP
-				case 6:
+				// WBMP
 				case 15:
 					$new_type = ($format & IMG_WBMP) ? IMG_WBMP : false;
 				break;