diff --git a/library/attach_mod/includes/functions_thumbs.php b/library/attach_mod/includes/functions_thumbs.php
index 984a71c99..6c44ba0cd 100644
--- a/library/attach_mod/includes/functions_thumbs.php
+++ b/library/attach_mod/includes/functions_thumbs.php
@@ -63,26 +63,24 @@ function get_supported_image_types($type)
     $new_type = 0;
 
     switch ($type) {
-        case 1:
+        case IMAGETYPE_GIF:
             $new_type = ($format & IMG_GIF) ? IMG_GIF : 0;
             break;
-        case 2:
-        case 9:
-        case 10:
-        case 11:
-        case 12:
+        case IMAGETYPE_JPEG:
+        case IMAGETYPE_JPC:
+        case IMAGETYPE_JP2:
+        case IMAGETYPE_JPX:
+        case IMAGETYPE_JB2:
             $new_type = ($format & IMG_JPG) ? IMG_JPG : 0;
             break;
-        case 3:
-        case 4:
+        case IMAGETYPE_PNG:
             $new_type = ($format & IMG_PNG) ? IMG_PNG : 0;
             break;
-        case 6:
-        case 8:
-        case 15:
+        case IMAGETYPE_BMP:
+        case IMAGETYPE_WBMP:
             $new_type = ($format & IMG_WBMP) ? IMG_WBMP : 0;
             break;
-        case 32:
+        case IMAGETYPE_WEBP:
             $new_type = ($format & IMG_WEBP) ? IMG_WEBP : 0;
             break;
     }