diff --git a/src/PHPSQLParser/processors/ColumnDefinitionProcessor.php b/src/PHPSQLParser/processors/ColumnDefinitionProcessor.php
index 1ab91574..1fd3f9ae 100644
--- a/src/PHPSQLParser/processors/ColumnDefinitionProcessor.php
+++ b/src/PHPSQLParser/processors/ColumnDefinitionProcessor.php
@@ -394,8 +394,13 @@ public function process($tokens) {
                     $parsed = $this->processExpressionList($trim);
 
                     $last = array_pop($expr);
-                    $last['sub_tree'] = array('expr_type' => ExpressionType::BRACKET_EXPRESSION, 'base_expr' => $trim,
-                                              'sub_tree' => $parsed);
+                    $last['sub_tree'] = array(
+                                            array(
+                                                'expr_type' => ExpressionType::BRACKET_EXPRESSION,
+                                                'base_expr' => $trim,
+                                                'sub_tree' => $parsed
+                                            )
+                                        );
                     $expr[] = $last;
                     $currCategory = $prevCategory;
                     break;