Fix namespace error in PDOManager

diff --git a/src/models/datasources/PdoManager.php b/src/models/datasources/PdoManager.php
index 559bafeaa..e01c701dd 100644
--- a/src/models/datasources/PdoManager.php
+++ b/src/models/datasources/PdoManager.php
@@ -124,7 +124,7 @@ class PdoManager extends DatasourceManager
         if (empty(self::$active_connections[$this->connect_string])) {
             try {
                 $this->pdo = new \PDO($db_host, $db_user, $db_password,
-                    [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]);
+                    [\PDO::ATTR_ERRMODE => \PDO::ERRMODE_EXCEPTION]);
                 self::$active_connections[$this->connect_string] = $this->pdo;
             } catch (\PDOException $e) {
                 $this->pdo = false;