diff --git a/mod/quiz/db/mysql.php b/mod/quiz/db/mysql.php
index 0cd3325aab7..fd4bb0b88ee 100644
--- a/mod/quiz/db/mysql.php
+++ b/mod/quiz/db/mysql.php
@@ -1039,16 +1039,20 @@ function quiz_upgrade($oldversion) {
         // The newgraded field must always point to a valid state
         modify_database("","UPDATE prefix_question_sessions SET newgraded = newest where newgraded = '0'");
 
-        // The following table is discussed in bug 5468
-        modify_database ("", "CREATE TABLE prefix_question_attempts (
-                                  id int(10) unsigned NOT NULL auto_increment,
-                                  modulename varchar(20) NOT NULL default 'quiz',
-                                  PRIMARY KEY  (id)
-                                ) TYPE=MyISAM COMMENT='Student attempts. This table gets extended by the modules';");
-        // create one entry for all the existing quiz attempts
-        modify_database ("", "INSERT INTO prefix_question_attempts (id)
-                                   SELECT uniqueid
-                                   FROM prefix_quiz_attempts;");
+        // Only perform this if hasn't been performed before (in MOODLE_16_STABLE branch - bug 5717)
+        $tables = $db->MetaTables('TABLES');
+        if (!in_array($CFG->prefix . 'question_attempts', $tables)) {
+            // The following table is discussed in bug 5468
+            modify_database ("", "CREATE TABLE prefix_question_attempts (
+                                      id int(10) unsigned NOT NULL auto_increment,
+                                      modulename varchar(20) NOT NULL default 'quiz',
+                                      PRIMARY KEY  (id)
+                                    ) TYPE=MyISAM COMMENT='Student attempts. This table gets extended by the modules';");
+            // create one entry for all the existing quiz attempts
+            modify_database ("", "INSERT INTO prefix_question_attempts (id)
+                                       SELECT uniqueid
+                                       FROM prefix_quiz_attempts;");
+        }
     }
 
     if ($oldversion < 2006060700) { // fix for 5720
diff --git a/mod/quiz/db/postgres7.php b/mod/quiz/db/postgres7.php
index f8fd7835536..0b5d5c66894 100644
--- a/mod/quiz/db/postgres7.php
+++ b/mod/quiz/db/postgres7.php
@@ -1211,15 +1211,19 @@ function quiz_upgrade($oldversion) {
         // The newgraded field must always point to a valid state
         modify_database("","UPDATE prefix_question_sessions SET newgraded = newest where newgraded = '0'");
 
-        // The following table is discussed in bug 5468
-        modify_database ("", "CREATE TABLE prefix_question_attempts (
-                                 id SERIAL PRIMARY KEY,
-                                 modulename varchar(20) NOT NULL default 'quiz'
-                              );");
-        // create one entry for all the existing quiz attempts
-        modify_database ("", "INSERT INTO prefix_question_attempts (id)
-                                   SELECT uniqueid
-                                   FROM prefix_quiz_attempts;");
+        // Only perform this if hasn't been performed before (in MOODLE_16_STABLE branch - bug 5717)
+        $tables = $db->MetaTables('TABLES');
+        if (!in_array($CFG->prefix . 'question_attempts', $tables)) {
+            // The following table is discussed in bug 5468
+            modify_database ("", "CREATE TABLE prefix_question_attempts (
+                                     id SERIAL PRIMARY KEY,
+                                     modulename varchar(20) NOT NULL default 'quiz'
+                                  );");
+            // create one entry for all the existing quiz attempts
+            modify_database ("", "INSERT INTO prefix_question_attempts (id)
+                                       SELECT uniqueid
+                                       FROM prefix_quiz_attempts;");
+        }
     }
 
     if ($oldversion < 2006051700) { // this block also exec'd by 2006042802 on MOODLE_16_STABLE