diff --git a/library/Director/IcingaConfig/ExtensibleSet.php b/library/Director/IcingaConfig/ExtensibleSet.php
index b68f0459..04106d1c 100644
--- a/library/Director/IcingaConfig/ExtensibleSet.php
+++ b/library/Director/IcingaConfig/ExtensibleSet.php
@@ -296,6 +296,16 @@ class ExtensibleSet
         return $this;
     }
 
+    protected function renderArray($array)
+    {
+        $safe = array();
+        foreach ($array as $value) {
+            $safe[] = c::alreadyRendered($value);
+        }
+
+        return c::renderArray($safe);
+    }
+
     public function renderAs($key, $prefix = '    ')
     {
         $parts = array();
@@ -303,7 +313,7 @@ class ExtensibleSet
         if ($this->ownValues !== null) {
             $parts[] = c::renderKeyValue(
                 $key,
-                c::renderArray($this->ownValues),
+                $this->renderArray($this->ownValues),
                 $prefix
             );
         }
@@ -312,7 +322,7 @@ class ExtensibleSet
             $parts[] = c::renderKeyOperatorValue(
                 $key,
                 '+=',
-                c::renderArray($this->plusValues),
+                $this->renderArray($this->plusValues),
                 $prefix
             );
         }
@@ -321,7 +331,7 @@ class ExtensibleSet
             $parts[] = c::renderKeyOperatorValue(
                 $key,
                 '-=',
-                c::renderArray($this->minusValues),
+                $this->renderArray($this->minusValues),
                 $prefix
             );
         }
diff --git a/test/php/library/Director/IcingaConfig/ExtensibleSetTest.php b/test/php/library/Director/IcingaConfig/ExtensibleSetTest.php
index 63f343d3..34bd83a3 100644
--- a/test/php/library/Director/IcingaConfig/ExtensibleSetTest.php
+++ b/test/php/library/Director/IcingaConfig/ExtensibleSetTest.php
@@ -146,13 +146,13 @@ class ExtensibleSetTest extends BaseTestCase
 
     public function testCombinedDefinitionRendersCorrectly()
     {
-        $set = new ExtensibleSet(array('pre', 'def', 'ined'));
-        $set->blacklist(array('and', 'not', 'those'));
-        $set->extend('plus this');
+        $set = new ExtensibleSet(array('Pre', 'Def', 'Ined'));
+        $set->blacklist(array('And', 'Not', 'Those'));
+        $set->extend('PlusThis');
 
-        $out = '    key_name = [ "pre", "def", "ined" ]' . "\n"
-             . '    key_name += [ "plus this" ]' . "\n"
-             . '    key_name -= [ "and", "not", "those" ]' . "\n";
+        $out = '    key_name = [ Pre, Def, Ined ]' . "\n"
+             . '    key_name += [ PlusThis ]' . "\n"
+             . '    key_name -= [ And, Not, Those ]' . "\n";
 
         $this->assertEquals(
             $out,