diff --git a/src/challenge-module.cpp b/src/challenge-module.cpp
index 59a0e58..371be25 100644
--- a/src/challenge-module.cpp
+++ b/src/challenge-module.cpp
@@ -30,6 +30,7 @@
 const std::string ChallengeModule::WAIT_SELECTION = "wait-selection";
 const std::string ChallengeModule::SUCCESS = "success";
 const std::string ChallengeModule::PENDING = "pending";
+const std::string ChallengeModule::FAILURE = "failure";
 
 ChallengeModule::ChallengeModule(const std::string& uniqueType)
   : CHALLENGE_TYPE(uniqueType)