diff --git a/src/protocol-detail/challenge.cpp b/src/protocol-detail/challenge.cpp
index 2923270..e4d5ecb 100644
--- a/src/protocol-detail/challenge.cpp
+++ b/src/protocol-detail/challenge.cpp
@@ -29,7 +29,7 @@
 CHALLENGE::encodeDataPayload(const CertificateRequest& request)
 {
   Block response = makeEmptyBlock(tlv_encrypted_payload);
-  response.push_back(makeNonNegativeIntegerBlock(tlv_status, request.m_status));
+  response.push_back(makeNonNegativeIntegerBlock(tlv_status, static_cast<size_t>(request.m_status)));
   response.push_back(makeStringBlock(tlv_challenge_status, request.m_challengeStatus));
   response.push_back(makeNonNegativeIntegerBlock(tlv_remaining_tries, request.m_remainingTries));
   response.push_back(makeNonNegativeIntegerBlock(tlv_remaining_time, request.m_remainingTime));