diff --git a/rtgui/thumbimageupdater.cc b/rtgui/thumbimageupdater.cc
index d8687e9ad..07b569b8c 100644
--- a/rtgui/thumbimageupdater.cc
+++ b/rtgui/thumbimageupdater.cc
@@ -69,9 +69,12 @@ public:
 		inactive_waiting_(false)
 	{
 		int threadCount=1;
+#if !(defined( WIN32 ) && defined( __x86_64__ ))
+		// See Issue 2431 for explanation
 		#ifdef _OPENMP
 			threadCount=omp_get_num_procs();
 		#endif
+#endif
 		
 		threadPool_=new Glib::ThreadPool(threadCount,0);
 	}