diff --git a/dblayer.php b/dblayer.php
index dbf1aa5..405a465 100644
--- a/dblayer.php
+++ b/dblayer.php
@@ -160,6 +160,9 @@ class dblayer extends PDO
       $this->exec("SET NAMES 'utf8'");
       $this->sep = "\"";
       break;
+    default:
+      throw new Exception (dgettext("domframework",
+                                    "Unknown PDO driver provided"), 500);
     }
     $this->dsn = $dsn;
   }
@@ -416,7 +419,8 @@ class dblayer extends PDO
         $select = array ();
         if ($updatekey !== false)
         {
-          if ($columns === $this->primary)
+          // This line have a problem to update a tuple with the same values
+          //  if ($columns === $this->primary)
             $select[] = array ($this->primary, $updatekey, "!=");
         }
         $select[] = array ($columns, $after[$columns]);