Index: include/lldb/Utility/TaskPool.h
===================================================================
--- include/lldb/Utility/TaskPool.h
+++ include/lldb/Utility/TaskPool.h
@@ -12,6 +12,7 @@
 
 #include <cassert>
 #include <cstdint>
+#include <functional>
 #include <future>
 #include <list>
 #include <queue>