diff --git a/mod/chat/db/upgrade.php b/mod/chat/db/upgrade.php
index 6c26cc3efec..b83e78c8774 100644
--- a/mod/chat/db/upgrade.php
+++ b/mod/chat/db/upgrade.php
@@ -48,7 +48,9 @@ function xmldb_chat_upgrade($oldversion) {
         $field = new xmldb_field('introformat', XMLDB_TYPE_INTEGER, '4', XMLDB_UNSIGNED, XMLDB_NOTNULL, null, '0', 'intro');
 
     /// Launch add field introformat
-        $dbman->add_field($table, $field);
+        if (!$dbman->field_exists($table, $field)) {
+            $dbman->add_field($table, $field);
+        }
 
     /// chat savepoint reached
         upgrade_mod_savepoint($result, 2010050101, 'chat');