diff --git a/src/handles/delete-handle.cpp b/src/handles/delete-handle.cpp
index c6ad7c5..5cd0506 100644
--- a/src/handles/delete-handle.cpp
+++ b/src/handles/delete-handle.cpp
@@ -92,7 +92,8 @@
 }
 
 void
-DeleteHandle::onValidationFailed(const shared_ptr<const Interest>& interest, const string& reason)
+DeleteHandle::onValidationFailed(const shared_ptr<const Interest>& interest,
+                                 const std::string& reason)
 {
   std::cerr << reason << std::endl;
   negativeReply(*interest, 401);