fix warnings

Change-Id: I23aa29d8cb2ddc77d86aee14c5e99f6c3945029b
diff --git a/tests/unit-tests/challenge-credential.t.cpp b/tests/unit-tests/challenge-credential.t.cpp
index 38b77bb..04347ab 100644
--- a/tests/unit-tests/challenge-credential.t.cpp
+++ b/tests/unit-tests/challenge-credential.t.cpp
@@ -53,7 +53,7 @@
   auto identityA = addIdentity(Name("/example"));
   auto keyA = identityA.getDefaultKey();
   auto certA = key.getDefaultCertificate();
-  RequestId requestId = {1,2,3,4,5,6,7,8};
+  RequestId requestId = {{1,2,3,4,5,6,7,8}};
   std::array<uint8_t, 16> aesKey;
   ca::RequestState state(Name("/example"), requestId, RequestType::NEW,
                          Status::BEFORE_CHALLENGE, certA, std::move(aesKey));