diff --git a/dblayeroo.php b/dblayeroo.php
index 1c32a60..eaa7ef3 100644
--- a/dblayeroo.php
+++ b/dblayeroo.php
@@ -2299,6 +2299,11 @@ class dblayeroo
   {
     $update = !! $update;
     $errors = array ();
+    if ($this->table === null)
+      throw new \Exception ("No table name defined", 500);
+    if ($this->primary === null)
+      throw new \Exception ("No primary key defined for table '$this->table'",
+                            500);
     if ($update === false)
     {
       // INSERT mode