diff --git a/form.php b/form.php
index 2178bc0..653d407 100644
--- a/form.php
+++ b/form.php
@@ -315,19 +315,29 @@ class formfield
       if (isset ($this->readonly) && $this->readonly !== FALSE)
         $res .= " disabled='disabled'";
       // Do not check by default !
-      // Check is enable if not null, false, 'unset' or ''
+      // Check is enable if not null and not false and not "unset" and not ""
       if (count ($this->titles) === 1)
       {
-        if (isset ($this->values) && $this->values !== "unset")
+        if (isset ($this->values) &&
+            $this->values !== null &&
+            $this->values !== false &&
+            $this->values !== "unset" &&
+            $this->values !== "")
           $res .= " checked='checked'";
-        elseif (count ($this->titles) === 1 && isset ($this->defaults) &&
-                $this->defaults !== null && $this->defaults !== false &&
-                $this->defaults !== "unset" && $this->defaults !== "")
+        elseif (isset ($this->defaults) &&
+                $this->defaults !== null &&
+                $this->defaults !== false &&
+                $this->defaults !== "unset" &&
+                $this->defaults !== "")
           $res .= " checked='checked'";
       }
       else
       {
-        if (isset ($this->values[$key]) && $this->values[$key] !== "unset")
+        if (isset ($this->values[$key]) &&
+            $this->values[$key] !== null &&
+            $this->values[$key] !== false &&
+            $this->values[$key] !== "unset" &&
+            $this->values[$key] !== "")
           $res .= " checked='checked'";
         elseif (isset ($this->defaults[$key]) && 
                 $this->defaults[$key] !== null &&