diff --git a/mod/assignment/mod.html b/mod/assignment/mod.html
index d9f54df115e..d0486f1b9d9 100644
--- a/mod/assignment/mod.html
+++ b/mod/assignment/mod.html
@@ -77,14 +77,18 @@
         <?
         $sizelist = array("10Kb", "50Kb", "100Kb", "500Kb", "1Mb", "2Mb", "5Mb", "10Mb", "20Mb", "50Mb");
         $maxsize = get_max_upload_file_size();
+        $sizeinlist = false;
         foreach ($sizelist as $size) {
             $sizebytes = get_real_size($size);
             if ($sizebytes < $maxsize) {
                 $filesize[$sizebytes] = $size;
             }
+            if ($form->maxbytes == $sizebytes) {
+                $sizeinlist = true;
+            }
         }
         $filesize[$maxsize] = display_size($maxsize);
-        if (!$form->maxbytes) {
+        if (!$sizeinlist) {
             $form->maxbytes = get_real_size("500K");
         }
         ksort($filesize, SORT_NUMERIC);