diff --git a/lib/dml/pgsql_native_moodle_database.php b/lib/dml/pgsql_native_moodle_database.php
index 44d298c03a6..a85023dc054 100644
--- a/lib/dml/pgsql_native_moodle_database.php
+++ b/lib/dml/pgsql_native_moodle_database.php
@@ -345,13 +345,15 @@ class pgsql_native_moodle_database extends moodle_database {
 
         if ($result) {
             while ($row = pg_fetch_assoc($result)) {
-                if (!preg_match('/CREATE (|UNIQUE )INDEX ([^\s]+) ON '.$tablename.' USING ([^\s]+) \(([^\)]+)\)/i', $row['indexdef'], $matches)) {
+                // The index definition could be generated schema-qualifying the target table name
+                // for safety, depending on the pgsql version (CVE-2018-1058).
+                if (!preg_match('/CREATE (|UNIQUE )INDEX ([^\s]+) ON (|'.$row['schemaname'].'\.)'.$tablename.' USING ([^\s]+) \(([^\)]+)\)/i', $row['indexdef'], $matches)) {
                     continue;
                 }
-                if ($matches[4] === 'id') {
+                if ($matches[5] === 'id') {
                     continue;
                 }
-                $columns = explode(',', $matches[4]);
+                $columns = explode(',', $matches[5]);
                 foreach ($columns as $k=>$column) {
                     $column = trim($column);
                     if ($pos = strpos($column, ' ')) {