diff --git a/internal/ceres/thread_pool.h b/internal/ceres/thread_pool.h
index 1ebb52e..cdf6625 100644
--- a/internal/ceres/thread_pool.h
+++ b/internal/ceres/thread_pool.h
@@ -37,6 +37,7 @@
 #include <vector>
 
 #include "ceres/concurrent_queue.h"
+#include "ceres/internal/port.h"
 
 namespace ceres {
 namespace internal {
@@ -57,7 +58,7 @@
 //  workers to stop.  The workers will finish all of the tasks that have already
 //  been added to the thread pool.
 //
-class ThreadPool {
+class CERES_EXPORT_INTERNAL ThreadPool {
  public:
   // Returns the maximum number of hardware threads.
   static int MaxNumThreadsAvailable();