diff --git a/sdk/Windows/SMXHelperThread.cpp b/sdk/Windows/SMXHelperThread.cpp
index bf3bd85..485c405 100644
--- a/sdk/Windows/SMXHelperThread.cpp
+++ b/sdk/Windows/SMXHelperThread.cpp
@@ -74,3 +74,8 @@ void SMX::SMXHelperThread::RunInThread(function<void()> func)
     SetEvent(m_hEvent->value());
     m_Lock.Unlock();
 }
+
+bool SMX::SMXHelperThread::IsCurrentThread() const
+{
+    return GetCurrentThreadId() == m_iThreadId;
+}
diff --git a/sdk/Windows/SMXHelperThread.h b/sdk/Windows/SMXHelperThread.h
index ceeffa1..18ad24d 100644
--- a/sdk/Windows/SMXHelperThread.h
+++ b/sdk/Windows/SMXHelperThread.h
@@ -26,9 +26,8 @@ public:
     // Call func asynchronously from the helper thread.
     void RunInThread(function<void()> func);
 
-    // Return the Win32 thread ID, or INVALID_HANDLE_VALUE if the thread has been
-    // shut down.
-    DWORD GetThreadId() const { return m_iThreadId; }
+    // Return true if this is the calling thread.
+    bool IsCurrentThread() const;
 
 private:
     static DWORD WINAPI ThreadMainStart(void *self_);
diff --git a/sdk/Windows/SMXManager.cpp b/sdk/Windows/SMXManager.cpp
index baa0593..90771de 100644
--- a/sdk/Windows/SMXManager.cpp
+++ b/sdk/Windows/SMXManager.cpp
@@ -71,7 +71,7 @@ void SMX::SMXManager::Shutdown()
 
     // Make sure we're not being called from within m_UserCallbackThread, since that'll
     // deadlock when we shut down m_UserCallbackThread.
-    if(m_UserCallbackThread.GetThreadId() == GetCurrentThreadId())
+    if(m_UserCallbackThread.IsCurrentThread())
         throw runtime_error("SMX::SMXManager::Shutdown must not be called from an SMX callback");
 
     // Shut down the thread we make user callbacks from.