diff --git a/mod/quiz/lib.php b/mod/quiz/lib.php
index a9f5e028a3b..c72b25cd1b0 100644
--- a/mod/quiz/lib.php
+++ b/mod/quiz/lib.php
@@ -1433,7 +1433,7 @@ function quiz_num_attempt_summary($quiz, $cm, $returnzero = false, $currentgroup
         if (groups_get_activity_groupmode($cm)) {
             $a->total = $numattempts;
             if ($currentgroup) {
-                $a->group = $DB->count_records_sql('SELECT count(1) FROM ' .
+                $a->group = $DB->count_records_sql('SELECT COUNT(DISTINCT qa.id) FROM ' .
                         '{quiz_attempts} qa JOIN ' .
                         '{groups_members} gm ON qa.userid = gm.userid ' .
                         'WHERE quiz = ? AND preview = 0 AND groupid = ?',
@@ -1441,7 +1441,7 @@ function quiz_num_attempt_summary($quiz, $cm, $returnzero = false, $currentgroup
                 return get_string('attemptsnumthisgroup', 'quiz', $a);
             } else if ($groups = groups_get_all_groups($cm->course, $USER->id, $cm->groupingid)) {
                 list($usql, $params) = $DB->get_in_or_equal(array_keys($groups));
-                $a->group = $DB->count_records_sql('SELECT count(1) FROM ' .
+                $a->group = $DB->count_records_sql('SELECT COUNT(DISTINCT qa.id) FROM ' .
                         '{quiz_attempts} qa JOIN ' .
                         '{groups_members} gm ON qa.userid = gm.userid ' .
                         'WHERE quiz = ? AND preview = 0 AND ' .