diff --git a/ipc/glue/MessageChannel.cpp b/ipc/glue/MessageChannel.cpp
index f4f6ba4be3f3..bd7fb8181230 100644
--- a/ipc/glue/MessageChannel.cpp
+++ b/ipc/glue/MessageChannel.cpp
@@ -717,7 +717,7 @@ MessageChannel::Clear()
 
     gUnresolvedPromises -= mPendingPromises.size();
     for (auto& pair : mPendingPromises) {
-        pair.second.mRejectFunction(pair.second.mPromise, __func__);
+        pair.second.mRejectFunction(__func__);
     }
     mPendingPromises.clear();
 
diff --git a/ipc/glue/MessageChannel.h b/ipc/glue/MessageChannel.h
index 5443727e433f..69d3225efebc 100644
--- a/ipc/glue/MessageChannel.h
+++ b/ipc/glue/MessageChannel.h
@@ -98,7 +98,7 @@ class MessageChannel : HasResultCodes, MessageLoop::DestructionObserver
     struct PromiseHolder
     {
         RefPtr<MozPromiseRefcountable> mPromise;
-        std::function<void(MozPromiseRefcountable*, const char*)> mRejectFunction;
+        std::function<void(const char*)> mRejectFunction;
     };
     static Atomic<size_t> gUnresolvedPromises;
     friend class PromiseReporter;
@@ -186,10 +186,8 @@ class MessageChannel : HasResultCodes, MessageLoop::DestructionObserver
         }
         PromiseHolder holder;
         holder.mPromise = aPromise;
-        holder.mRejectFunction = [](MozPromiseRefcountable* aPromise,
-                                    const char* aRejectSite) {
-            static_cast<Promise*>(aPromise)->Reject(
-                PromiseRejectReason::ChannelClosed, aRejectSite);
+        holder.mRejectFunction = [aPromise](const char* aRejectSite) {
+            aPromise->Reject(PromiseRejectReason::ChannelClosed, aRejectSite);
         };
         mPendingPromises.insert(std::make_pair(seqno, Move(holder)));
         gUnresolvedPromises++;
diff --git a/ipc/ipdl/test/cxx/TestAsyncReturns.cpp b/ipc/ipdl/test/cxx/TestAsyncReturns.cpp
index f34b46a9b269..12c6c4a7a37e 100644
--- a/ipc/ipdl/test/cxx/TestAsyncReturns.cpp
+++ b/ipc/ipdl/test/cxx/TestAsyncReturns.cpp
@@ -2,8 +2,6 @@
 
 #include "IPDLUnitTests.h"      // fail etc.
 
-#include "mozilla/Unused.h"
-
 namespace mozilla {
 namespace _ipdltest {
 
@@ -81,7 +79,7 @@ mozilla::ipc::IPCResult
 TestAsyncReturnsChild::RecvNoReturn(RefPtr<NoReturnPromise>&& aPromise)
 {
   // Leak the promise intentionally
-  Unused << do_AddRef(aPromise);
+  aPromise->AddRef();
   return IPC_OK();
 }