diff --git a/core/imageboard.pack.php b/core/imageboard.pack.php
index 249b1b2f..0b2c89b8 100644
--- a/core/imageboard.pack.php
+++ b/core/imageboard.pack.php
@@ -972,7 +972,8 @@ function move_upload_to_archive($event) {
 	$target = warehouse_path("images", $event->hash);
 	if(!file_exists(dirname($target))) mkdir(dirname($target), 0755, true);
 	if(!@copy($event->tmpname, $target)) {
-		throw new UploadException("Failed to copy file from uploads ({$event->tmpname}) to archive ($target)");
+		$errors = error_get_last(); // note: requires php 5.2
+		throw new UploadException("Failed to copy file from uploads ({$event->tmpname}) to archive ($target): {$errors['type']} / {$errors['message']}");
 		return false;
 	}
 	return true;