diff --git a/src/identity-challenge/challenge-module.cpp b/src/identity-challenge/challenge-module.cpp
index 0570ed5..03feeeb 100644
--- a/src/identity-challenge/challenge-module.cpp
+++ b/src/identity-challenge/challenge-module.cpp
@@ -77,7 +77,7 @@
 {
   request.m_status = Status::FAILURE;
   request.m_challengeType = "";
-  request.m_challengeState = boost::none;
+  request.m_challengeState = nullopt;
   return std::make_tuple(errorCode, std::move(errorInfo));
 }
 
@@ -96,7 +96,7 @@
 {
   request.m_status = Status::PENDING;
   request.m_challengeType = CHALLENGE_TYPE;
-  request.m_challengeState = boost::none;
+  request.m_challengeState = nullopt;
   return std::make_tuple(ErrorCode::NO_ERROR, "");
 }