diff --git a/src/Model/Database.php b/src/Model/Database.php
index d148c6c..d9f7175 100644
--- a/src/Model/Database.php
+++ b/src/Model/Database.php
@@ -7,7 +7,7 @@ class Database
     /**
      * @var Table[]
      */
-    private $tables;
+    private $tables = [];
 
     /**
      * @return Table[]
diff --git a/src/Model/Table.php b/src/Model/Table.php
index 96a6c40..f1ebbc9 100644
--- a/src/Model/Table.php
+++ b/src/Model/Table.php
@@ -32,7 +32,7 @@ class Table
     /**
      * @var Column[]
      */
-    private $primaryKeys;
+    private $primaryKeys = [];
 
     /**
      * @var ForeignKey[]