diff --git a/daemon/mgmt/command-authenticator.cpp b/daemon/mgmt/command-authenticator.cpp
index 6f85fc7..04f2476 100644
--- a/daemon/mgmt/command-authenticator.cpp
+++ b/daemon/mgmt/command-authenticator.cpp
@@ -51,12 +51,12 @@
 
 /** \brief obtain signer from SignerTag attached to Interest, if available
  */
-static ndn::optional<std::string>
+static optional<std::string>
 getSignerFromTag(const Interest& interest)
 {
   shared_ptr<SignerTag> signerTag = interest.getTag<SignerTag>();
   if (signerTag == nullptr) {
-    return ndn::nullopt;
+    return nullopt;
   }
   else {
     return signerTag->get().toUri();