diff --git a/library/Director/IcingaConfig/ExtensibleSet.php b/library/Director/IcingaConfig/ExtensibleSet.php
index 3c8f7fc4..1addfee3 100644
--- a/library/Director/IcingaConfig/ExtensibleSet.php
+++ b/library/Director/IcingaConfig/ExtensibleSet.php
@@ -3,6 +3,7 @@
 namespace Icinga\Module\Director\IcingaConfig;
 
 use Icinga\Exception\InvalidPropertyException;
+use Icinga\Module\Director\IcingaConfig\IcingaConfigHelper as c;
 
 class ExtensibleSet
 {
@@ -89,6 +90,38 @@ class ExtensibleSet
         return $this;
     }
 
+    public function renderAs($key, $prefix = '    ')
+    {
+        $parts = array();
+
+        if ($this->ownValues !== null) {
+            $parts[] = c::renderKeyValue(
+                $key,
+                c::renderArray($this->ownValues),
+                $prefix
+            );
+        }
+
+        if (! empty($this->plusValues)) {
+            $parts[] = c::renderKeyOperatorValue(
+                $key,
+                '+=',
+                c::renderArray($this->plusValues),
+                $prefix
+            );
+        }
+        if (! empty($this->minusValues)) {
+            $parts[] = c::renderKeyOperatorValue(
+                $key,
+                '-=',
+                c::renderArray($this->plusValues),
+                $prefix
+            );
+        }
+
+        return implode('', $parts);
+    }
+
     protected function hasBeenResolved()
     {
         return $this->resolvedValues !== null;
diff --git a/test/php/library/Director/IcingaConfig/ExtensibleSetTest.php b/test/php/library/Director/IcingaConfig/ExtensibleSetTest.php
index f1fa189b..23fbad73 100644
--- a/test/php/library/Director/IcingaConfig/ExtensibleSetTest.php
+++ b/test/php/library/Director/IcingaConfig/ExtensibleSetTest.php
@@ -132,4 +132,20 @@ class ExtensibleSetTest extends BaseTestCase
             $child->getResolvedValues()
         );
     }
+
+    public function testCombinedDefinitionRendersCorrectly()
+    {
+        $set = new ExtensibleSet(array('pre', 'def', 'ined'));
+        $set->blacklist('and', 'not', 'those');
+        $set->extend('plus this');
+
+        $out = '    key_name = [ "pre", "def", "ined" ]' . "\n"
+             . '    key_name += [ "plus this" ]' . "\n"
+             . '    key_name -= [ "plus this" ]' . "\n";
+
+        $this->assertEquals(
+            $out,
+            $set->renderAs('key_name')
+        );
+    }
 }