diff --git a/plugins/libkolab/lib/kolab_format.php b/plugins/libkolab/lib/kolab_format.php
index 4c8e363b..a7b1e487 100644
--- a/plugins/libkolab/lib/kolab_format.php
+++ b/plugins/libkolab/lib/kolab_format.php
@@ -158,6 +158,40 @@ abstract class kolab_format
         return $vec;
     }
 
+    /**
+     * Check for format errors after calling kolabformat::write*()
+     *
+     * @return boolean True if there were errors, False if OK
+     */
+    protected function format_errors()
+    {
+        $ret = $log = false;
+        switch (kolabformat::error()) {
+            case kolabformat.NoError:
+                $ret = false;
+                break;
+            case kolabformat.Warning:
+                $ret = false;
+                $log = "Warning";
+                break;
+            default:
+                $ret = true;
+                $log = "Error";
+        }
+
+        if ($log) {
+            raise_error(array(
+                'code' => 660,
+                'type' => 'php',
+                'file' => __FILE__,
+                'line' => __LINE__,
+                'message' => "kolabformat write $log: " . kolabformat::errorMessage(),
+            ), true);
+        }
+
+        return $ret;
+    }
+
     /**
      * Save the last generated UID to the object properties.
      * Should be called after kolabformat::writeXXXX();
diff --git a/plugins/libkolab/lib/kolab_format_contact.php b/plugins/libkolab/lib/kolab_format_contact.php
index 1f20e3e1..d6da2352 100644
--- a/plugins/libkolab/lib/kolab_format_contact.php
+++ b/plugins/libkolab/lib/kolab_format_contact.php
@@ -132,11 +132,12 @@ class kolab_format_contact extends kolab_format
     public function write()
     {
         $this->init();
+        $this->xmldata = kolabformat::writeContact($this->obj);
 
-        if ($this->obj->isValid()) {
-            $this->xmldata = kolabformat::writeContact($this->obj);
+        if (!parent::format_errors())
             parent::update_uid();
-        }
+        else
+            $this->xmldata = null;
 
         return $this->xmldata;
     }
diff --git a/plugins/libkolab/lib/kolab_format_distributionlist.php b/plugins/libkolab/lib/kolab_format_distributionlist.php
index b8d22085..592387e2 100644
--- a/plugins/libkolab/lib/kolab_format_distributionlist.php
+++ b/plugins/libkolab/lib/kolab_format_distributionlist.php
@@ -51,11 +51,12 @@ class kolab_format_distributionlist extends kolab_format
     public function write()
     {
         $this->init();
+        $this->xmldata = kolabformat::writeDistlist($this->obj);
 
-        if ($this->obj->isValid()) {
-            $this->xmldata = kolabformat::writeDistlist($this->obj);
+        if (!parent::format_errors())
             parent::update_uid();
-        }
+        else
+            $this->xmldata = null;
 
         return $this->xmldata;
     }
diff --git a/plugins/libkolab/lib/kolab_format_event.php b/plugins/libkolab/lib/kolab_format_event.php
index 42c323c3..c2c0ddf6 100644
--- a/plugins/libkolab/lib/kolab_format_event.php
+++ b/plugins/libkolab/lib/kolab_format_event.php
@@ -116,11 +116,12 @@ class kolab_format_event extends kolab_format
     public function write()
     {
         $this->init();
+        $this->xmldata = kolabformat::writeEvent($this->obj);
 
-        if ($this->obj->isValid()) {
-            $this->xmldata = kolabformat::writeEvent($this->obj);
+        if (!parent::format_errors())
             parent::update_uid();
-        }
+        else
+            $this->xmldata = null;
 
         return $this->xmldata;
     }