--- a/dom/u2f/U2F.cpp
+++ b/dom/u2f/U2F.cpp
@@ -14,17 +14,16 @@
 
 namespace mozilla {
 namespace dom {
 
 static mozilla::LazyLogModule gU2FLog("u2fmanager");
 
 NS_NAMED_LITERAL_STRING(kFinishEnrollment, "navigator.id.finishEnrollment");
 NS_NAMED_LITERAL_STRING(kGetAssertion, "navigator.id.getAssertion");
-NS_NAMED_LITERAL_STRING(kRequiredU2FVersion, "U2F_V2");
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(U2F)
   NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
   NS_INTERFACE_MAP_ENTRY(nsISupports)
 NS_INTERFACE_MAP_END
 
 NS_IMPL_CYCLE_COLLECTING_ADDREF(U2F)
 NS_IMPL_CYCLE_COLLECTING_RELEASE(U2F)

--- a/dom/u2f/U2FAuthenticator.h
+++ b/dom/u2f/U2FAuthenticator.h
@@ -21,12 +21,14 @@ enum class ErrorCode {
   BAD_REQUEST = 2,
   CONFIGURATION_UNSUPPORTED = 3,
   DEVICE_INELIGIBLE = 4,
   TIMEOUT = 5
 };
 
 typedef MozPromise<nsString, ErrorCode, false> U2FPromise;
 
+NS_NAMED_LITERAL_STRING(kRequiredU2FVersion, "U2F_V2");
+
 } // namespace dom
 } // namespace mozilla
 
 #endif // mozilla_dom_U2FAuthenticator_h

--- a/dom/u2f/U2FManager.cpp
+++ b/dom/u2f/U2FManager.cpp
@@ -352,16 +352,17 @@ U2FManager::FinishRegister(nsTArray<uint
   if (NS_WARN_IF(NS_FAILED(rvClientData)) ||
       NS_WARN_IF(NS_FAILED(rvRegistrationData))) {
     mTransactionPromise.Reject(ErrorCode::OTHER_ERROR, __func__);
     return;
   }
 
   // Assemble a response object to return
   RegisterResponse response;
+  response.mVersion.Construct(kRequiredU2FVersion);
   response.mClientData.Construct(clientDataBase64);
   response.mRegistrationData.Construct(registrationDataBase64);
   response.mErrorCode.Construct(static_cast<uint32_t>(ErrorCode::OK));
 
   nsString responseStr;
   if (NS_WARN_IF(!response.ToJSON(responseStr))) {
     mTransactionPromise.Reject(ErrorCode::OTHER_ERROR, __func__);
     return;

--- a/dom/u2f/tests/frame_register.html
+++ b/dom/u2f/tests/frame_register.html
@@ -14,16 +14,19 @@ var challenge = new Uint8Array(16);
 async function doTests() {
   local_is(window.location.origin, "https://example.com", "Is loaded correctly");
 
   // basic check
   await promiseU2FRegister("https://example.com/appId", [{
     version: version,
     challenge: bytesToBase64UrlSafe(challenge),
   }], [], function(res){
+    local_is(res.version, version, "Version should be set correctly");
+    local_ok(res.clientData.length > 0, "ClientData must be set");
+    local_ok(res.registrationData.length > 0, "RegistrationData must be set");
     local_is(res.errorCode, 0, "AppID should work from the domain");
   });
 
   await promiseU2FRegister("https://example.net/appId", [{
     version: version,
     challenge: bytesToBase64UrlSafe(challenge),
   }], [], function(res){
     local_is(res.errorCode, 2, "AppID should not work from other domains");