diff --git a/ServiceBinding/RpcLiteralRequestMessageBinder.php b/ServiceBinding/RpcLiteralRequestMessageBinder.php
index edef394..edcaecc 100644
--- a/ServiceBinding/RpcLiteralRequestMessageBinder.php
+++ b/ServiceBinding/RpcLiteralRequestMessageBinder.php
@@ -96,7 +96,9 @@ class RpcLiteralRequestMessageBinder implements MessageBinderInterface
                 $value = $p->getValue($message);
             }
 
-            $value = $this->processType($type->getValue(), $value);
+            if ($value !== null) {
+                $value = $this->processType($type->getValue(), $value);
+            }
 
             if (!$type->isNillable() && null === $value) {
                 throw new \SoapFault('SOAP_ERROR_COMPLEX_TYPE', sprintf('"%s:%s" cannot be null.', ucfirst(Wsdl::translateType($phpType)), $type->getName()));
diff --git a/ServiceBinding/RpcLiteralResponseMessageBinder.php b/ServiceBinding/RpcLiteralResponseMessageBinder.php
index 5cb6310..f894d97 100644
--- a/ServiceBinding/RpcLiteralResponseMessageBinder.php
+++ b/ServiceBinding/RpcLiteralResponseMessageBinder.php
@@ -82,7 +82,11 @@ class RpcLiteralResponseMessageBinder implements MessageBinderInterface
                 $p->setAccessible(true);
                 $value = $p->getValue($message);
 
-                $p->setValue($message, $this->processType($type->getValue(), $value));
+                if ($value !== null) {
+                    $value = $this->processType($type->getValue(), $value);
+                }
+
+                $p->setValue($message, $value);
             }
 
             if (!$type->isNillable() && null === $value) {