Add a necessary include file.

diff --git a/include/deal.II/base/thread_local_storage.h b/include/deal.II/base/thread_local_storage.h
index 10a9388b305049832c9c9a5bef154c82e6a7f43a..115df60ad7b312a1279436d66bbaee8aa64e998e 100644 (file)
--- a/include/deal.II/base/thread_local_storage.h
+++ b/include/deal.II/base/thread_local_storage.h
@@ -24,6 +24,7 @@
 #  include <list>
 #  include <map>
 #  include <memory>
+#  include <mutex>
 #  include <shared_mutex>
 #  include <thread>
 #  include <vector>