diff --git a/similarity/similarity_sources.class.php b/similarity/similarity_sources.class.php
index 43dc4a01b73b0f76d63a9fcec2c466f334b3cab5..cf467db7839164353cddece9388baad292abaa45 100644
--- a/similarity/similarity_sources.class.php
+++ b/similarity/similarity_sources.class.php
@@ -293,15 +293,15 @@ class vpl_similarity_preprocess {
     static public function activity(&$simil, $vpl, $filesselected = array(), $allfiles, $joinedfiles, $spb) {
         $vpl->require_capability( VPL_SIMILARITY_CAPABILITY );
         $cm = $vpl->get_course_module();
-        $groupmode = groups_get_activity_groupmode( $cm );
-        if (! $groupmode) {
-            $groupmode = groups_get_course_groupmode( $vpl->get_course() );
-        }
         $currentgroup = groups_get_activity_group( $cm, true );
         if (! $currentgroup) {
             $currentgroup = '';
         }
-        $list = $vpl->get_students($currentgroup);
+        if ($vpl->is_group_activity()) {
+            $list = groups_get_all_groups($vpl->get_course()->id, 0, $cm->groupingid);
+        } else {
+            $list = $vpl->get_students( $currentgroup );
+        }
         if (count( $list ) == 0) {
             return;
         }