--- a/ipc/mscom/EnsureMTA.h
+++ b/ipc/mscom/EnsureMTA.h
@@ -21,16 +21,26 @@
 
 namespace mozilla {
 namespace mscom {
 
 // This class is OK to use as a temporary on the stack.
 class MOZ_STACK_CLASS EnsureMTA
 {
 public:
+  /**
+   * This constructor just ensures that the MTA thread is up and running.
+   */
+  EnsureMTA()
+  {
+    MOZ_ASSERT(NS_IsMainThread());
+    nsCOMPtr<nsIThread> thread = GetMTAThread();
+    MOZ_ASSERT(thread);
+  }
+
   template <typename FuncT>
   EnsureMTA(const FuncT& aClosure)
   {
     MOZ_ASSERT(NS_IsMainThread());
     if (IsCurrentThreadMTA()) {
       // We're already on the MTA, we can run aClosure directly
       aClosure();
       return;