diff --git a/lldb/include/lldb/Target/Process.h b/lldb/include/lldb/Target/Process.h
--- a/lldb/include/lldb/Target/Process.h
+++ b/lldb/include/lldb/Target/Process.h
@@ -50,6 +50,7 @@
 #include "lldb/lldb-private.h"
 
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/Support/Threading.h"
 #include "llvm/Support/VersionTuple.h"
 
 namespace lldb_private {
@@ -2741,7 +2742,7 @@
   enum { eCanJITDontKnow = 0, eCanJITYes, eCanJITNo } m_can_jit;
   
   std::unique_ptr<UtilityFunction> m_dlopen_utility_func_up;
-  std::once_flag m_dlopen_utility_func_flag_once;
+  llvm::once_flag m_dlopen_utility_func_flag_once;
 
   size_t RemoveBreakpointOpcodesFromBuffer(lldb::addr_t addr, size_t size,
                                            uint8_t *buf) const;
diff --git a/lldb/tools/debugserver/source/MacOSX/DarwinLog/DarwinLogCollector.cpp b/lldb/tools/debugserver/source/MacOSX/DarwinLog/DarwinLogCollector.cpp
--- a/lldb/tools/debugserver/source/MacOSX/DarwinLog/DarwinLogCollector.cpp
+++ b/lldb/tools/debugserver/source/MacOSX/DarwinLog/DarwinLogCollector.cpp
@@ -46,7 +46,7 @@
     s_os_activity_stream_set_event_handler;
 
 bool LookupSPICalls() {
-  static std::once_flag s_once_flag;
+  static llvm::once_flag s_once_flag;
   static bool s_has_spi;
 
   std::call_once(s_once_flag, [] {