diff --git a/lib/dbh/dbh.class.php b/lib/dbh/dbh.class.php
index 6574c38500..51da790e16 100644
--- a/lib/dbh/dbh.class.php
+++ b/lib/dbh/dbh.class.php
@@ -437,10 +437,10 @@ class dbh
                 }
                 elseif(stripos($sql, 'CREATE UNIQUE INDEX') === 0 || stripos($sql, 'CREATE INDEX') === 0)
                 {
-                    preg_match('/ON\s+[^.`\s]+\.`([^\s`]+)`/', $sql, $matches);
+                    preg_match('/ON\s+([^.`\s]+\.)?`([^\s`]+)`/', $sql, $matches);
 
-                    $tableName = str_replace($this->config->prefix, '', $matches);
-                    $sql       = preg_replace('/INDEX\ +\`/', 'INDEX `' . strtolower($tableName[1]) . '_', $sql);
+                    $tableName = isset($matches[2]) ? str_replace($this->config->prefix, '', $matches[2]) : '';
+                    $sql       = preg_replace('/INDEX\ +\`/', 'INDEX `' . strtolower($tableName) . '_', $sql);
                 }
             case 'ALTER':
                 $sql = $this->formatField($sql);