diff --git a/src/identity-challenge/challenge-module.hpp b/src/identity-challenge/challenge-module.hpp
index 0f0d0b8..c12b03c 100644
--- a/src/identity-challenge/challenge-module.hpp
+++ b/src/identity-challenge/challenge-module.hpp
@@ -39,7 +39,7 @@
   {
     ChallengeFactory& factory = getFactory();
     BOOST_ASSERT(factory.count(typeName) == 0);
-    factory[typeName] = [] { return make_unique<ChallengeType>(); };
+    factory[typeName] = [] { return std::make_unique<ChallengeType>(); };
   }
 
   static bool