diff --git a/main/exercice/exercise_submit.php b/main/exercice/exercise_submit.php
index d644f27151..027badd3a8 100755
--- a/main/exercice/exercise_submit.php
+++ b/main/exercice/exercise_submit.php
@@ -50,12 +50,8 @@ if ($showGlossary) {
$htmlHeadXtra[] = api_get_js('jquery.highlight.js');
}
-$htmlHeadXtra[] = '';
-$htmlHeadXtra[] = '';
+$htmlHeadXtra[] = api_get_js('jquery.jsPlumb.all.js');
+$htmlHeadXtra[] = api_get_js('d3/jquery.xcolor.js');
//This library is necessary for the time control feature
$htmlHeadXtra[] = api_get_css(api_get_path(WEB_LIBRARY_PATH).'javascript/epiclock/stylesheet/jquery.epiclock.css');