diff --git a/features/file-upload.xml b/features/file-upload.xml
index 1b8b2fe461..30e219b1ce 100644
--- a/features/file-upload.xml
+++ b/features/file-upload.xml
@@ -326,7 +326,10 @@ foreach ($_FILES["pictures"]["error"] as $key => $error) {
UPLOAD_ERR_EXTENSION
- Value: 8; File upload stopped by extension. Introduced in PHP 5.2.0.
+ Value: 8; A PHP extension stopped the file upload. PHP does not
+ provide a way to ascertain which extension caused the file upload to
+ stop; examining the list of loaded extensions with phpinfo() may help.
+ Introduced in PHP 5.2.0.