diff --git a/src/Propel/Runtime/Connection/PdoConnection.php b/src/Propel/Runtime/Connection/PdoConnection.php
index ccbe947c9d..f883097550 100644
--- a/src/Propel/Runtime/Connection/PdoConnection.php
+++ b/src/Propel/Runtime/Connection/PdoConnection.php
@@ -51,7 +51,8 @@ public function __construct($dsn, $user = null, $password = null, array $options
         $pdoOptions = [];
         if (is_array($options)) {
             foreach ($options as $key => $option) {
-                $pdoOptions[constant('self::' . $key)] = $option;
+                $index = (is_numeric($key)) ? $key : constant('self::' . $key);
+                $pdoOptions[$index] = $option;
             }
         }