diff --git a/src/detail/challenge-encoder.hpp b/src/detail/challenge-encoder.hpp
index ab1fe8f..d0ad429 100644
--- a/src/detail/challenge-encoder.hpp
+++ b/src/detail/challenge-encoder.hpp
@@ -31,7 +31,7 @@
 {
 public:
   static Block
-  encodeDataContent(const ca::RequestState& request, optional<Name> issuedCertName = nullopt);
+  encodeDataContent(ca::RequestState& request, optional<Name> issuedCertName = nullopt);
 
   static void
   decodeDataContent(const Block& data, requester::RequestContext& state);