diff --git a/Soap/SoapResponse.php b/Soap/SoapResponse.php
index cb9c9a3..5fba41b 100644
--- a/Soap/SoapResponse.php
+++ b/Soap/SoapResponse.php
@@ -39,6 +39,17 @@ class SoapResponse extends Response
         $this->setReturnValue($returnValue);
     }
 
+    /**
+     * @param SoapHeader $soapHeader
+     */
+    public function addSoapHeader(SoapHeader $soapHeader)
+    {
+        $this->soapHeaders->add($soapHeader);
+    }
+
+    /**
+     * @return \BeSimple\SoapBundle\Util\Collection
+     */
     public function getSoapHeaders()
     {
         return $this->soapHeaders;
diff --git a/Util/Collection.php b/Util/Collection.php
index 60b1256..4ea5699 100644
--- a/Util/Collection.php
+++ b/Util/Collection.php
@@ -28,8 +28,7 @@ class Collection implements \IteratorAggregate, \Countable
             throw new \InvalidArgumentException(sprintf('Cannot add class "%s" because it is not an instance of "%s"', get_class($element), $this->class));
         }
 
-        $getter = $this->getter;
-        $this->elements[$element->$getter()] = $element;
+        $this->elements[$element->{$this->getter}()] = $element;
     }
 
     public function addAll($elements)