diff --git a/framework/yii/db/Migration.php b/framework/yii/db/Migration.php
index ae25914..38b1bdc 100644
--- a/framework/yii/db/Migration.php
+++ b/framework/yii/db/Migration.php
@@ -318,7 +318,7 @@ class Migration extends \yii\base\Component
 	 */
 	public function addPrimaryKey($name, $table, $columns)
 	{
-		echo "    > add primary key $name on $table (".is_array($columns) ? implode(',',$columns) : $columns.") ...";
+		echo "    > add primary key $name on $table (".(is_array($columns) ? implode(',',$columns) : $columns).") ...";
 		$time = microtime(true);
 		$this->db->createCommand()->addPrimaryKey($name, $table, $columns)->execute();
 		echo " done (time: " . sprintf('%.3f', microtime(true) - $time) . "s)\n";