diff --git a/dblayer.php b/dblayer.php
index ed262aa..03fae1f 100644
--- a/dblayer.php
+++ b/dblayer.php
@@ -738,7 +738,11 @@ class dblayer
         // name is 'group'
         // Don't put single quotes : don't work with SQLite
         // TODO : Test for PostgreSQL (Tested for SQLite and MySQL)
-        $req .= " $this->sep".$s[0]."$this->sep ".$s[2]." :".md5 ($s[0].$s[1]);
+        if ($s[1] !== null)
+          $req .= " $this->sep".$s[0]."$this->sep ".$s[2]." :".
+                  md5 ($s[0].$s[1]);
+        else
+          $req .= " $this->sep".$s[0]."$this->sep IS NULL";
       }
       $req .=")";
     }
@@ -795,6 +799,8 @@ class dblayer
     {
       foreach ($select as $s)
       {
+        if ($s[1] === null)
+          continue;
         if ($this->debug) echo "DEBUG BIND : ".$s[0]."(".md5 ($s[0].$s[1]).")->".
                                var_export ($s[1], TRUE)."\n";
         $st->bindValue (":".md5 ($s[0].$s[1]), $s[1]);