diff --git a/library/Director/CustomVariable/CustomVariable.php b/library/Director/CustomVariable/CustomVariable.php
index bfa6e617..50b47f55 100644
--- a/library/Director/CustomVariable/CustomVariable.php
+++ b/library/Director/CustomVariable/CustomVariable.php
@@ -39,14 +39,24 @@ abstract class CustomVariable
         return $this->type;
     }
 
+    public function getKey()
+    {
+        return $this->key;
+    }
+
+    public function getValue()
+    {
+        return $this->value;
+    }
+
     public function setValue($value)
     {
         if ($value instanceof CustomVariable) {
             if (! $this->equals($value)) {
-                $this->reallySet($value);
+                $this->reallySetValue($value);
             }
         } elseif ($value !== $this->value) {
-            $this->reallySet($value);
+            $this->reallySetValue($value);
         }
 
         return $this;
@@ -87,7 +97,7 @@ abstract class CustomVariable
 
         } elseif (is_array($value)) {
 
-            foreach (array_keys($value) as & $key) {
+            foreach (array_keys($value) as $key) {
                 if (! is_int($key) || ctype_digit($key)) {
                     return new CustomVariableDictionary($key, $value);
                 }
diff --git a/library/Director/CustomVariable/CustomVariables.php b/library/Director/CustomVariable/CustomVariables.php
index 7ca9a155..e15f91bd 100644
--- a/library/Director/CustomVariable/CustomVariables.php
+++ b/library/Director/CustomVariable/CustomVariables.php
@@ -22,12 +22,11 @@ class CustomVariables
     {
         $key = (string) $key;
 
-        // TODO: add support for null values
-        if ($value === null) {
-            unset($this->$key);
+        if (! $value instanceof CustomVariable) {
+            $value = CustomVariable::create($key, $value);
         }
 
-        if ($value === $this->get($key)) {
+        if (isset($this->$key) && $value->equals($this->get($key))) {
             return $this;
         }
 
@@ -37,6 +36,15 @@ class CustomVariables
         return $this;
     }
 
+    public function get($key)
+    {
+        if (array_key_exists($key, $this->vars)) {
+            return $this->vars[$key];
+        }
+
+        return null;
+    }
+
     public function hasBeenModified()
     {
         return $this->modified;
@@ -54,7 +62,7 @@ class CustomVariables
         $out = '';
 
         foreach ($this->vars as $key => $var) {
-            $out .= $var->toConfigString()
+            $out .= $var->toConfigString();
         }
 
         return $out;
@@ -85,7 +93,7 @@ class CustomVariables
      */
     public function __isset($key)
     {
-        return array_key_exists($key, $this->properties);
+        return array_key_exists($key, $this->vars);
     }
 
     /**
diff --git a/library/Director/Objects/IcingaObject.php b/library/Director/Objects/IcingaObject.php
index 6d3c1154..2eee1fe9 100644
--- a/library/Director/Objects/IcingaObject.php
+++ b/library/Director/Objects/IcingaObject.php
@@ -18,6 +18,8 @@ abstract class IcingaObject extends DbObject
 
     private $type;
 
+    private $vars;
+
     public function supportsCustomVars()
     {
         return $this->supportsCustomVars;
@@ -100,6 +102,10 @@ abstract class IcingaObject extends DbObject
             }
         }
 
+        if ($this->supportsCustomVars()) {
+            $out .= $this->vars()->toConfigString();
+        }
+
         return $out;
     }