diff --git a/src/identity-challenge/challenge-pin.hpp b/src/identity-challenge/challenge-pin.hpp
index 10b23d4..757870d 100644
--- a/src/identity-challenge/challenge-pin.hpp
+++ b/src/identity-challenge/challenge-pin.hpp
@@ -55,12 +55,12 @@
   handleChallengeRequest(const Block& params, ca::RequestState& request) override;
 
   // For Client
-  std::vector<std::tuple<std::string, std::string>>
+  std::multimap<std::string, std::string>
   getRequestedParameterList(Status status, const std::string& challengeStatus) override;
 
   Block
   genChallengeRequestTLV(Status status, const std::string& challengeStatus,
-                         std::vector<std::tuple<std::string, std::string>>&& params) override;
+                         std::multimap<std::string, std::string>&& params) override;
 
   // challenge status
   static const std::string NEED_CODE;