diff --git a/lldb/source/Plugins/Platform/MacOSX/PlatformAppleSimulator.cpp b/lldb/source/Plugins/Platform/MacOSX/PlatformAppleSimulator.cpp
index aecf9ae24d08..772b1f3c8977 100644
--- a/lldb/source/Plugins/Platform/MacOSX/PlatformAppleSimulator.cpp
+++ b/lldb/source/Plugins/Platform/MacOSX/PlatformAppleSimulator.cpp
@@ -24,6 +24,7 @@
 #include "lldb/Utility/LLDBAssert.h"
 #include "lldb/Utility/PseudoTerminal.h"
 #include "lldb/Utility/StreamString.h"
+#include "llvm/Support/Threading.h"
 
 using namespace lldb;
 using namespace lldb_private;
diff --git a/lldb/tools/debugserver/source/MacOSX/DarwinLog/DarwinLogCollector.cpp b/lldb/tools/debugserver/source/MacOSX/DarwinLog/DarwinLogCollector.cpp
index 56033cc205d9..9c81851c4443 100644
--- a/lldb/tools/debugserver/source/MacOSX/DarwinLog/DarwinLogCollector.cpp
+++ b/lldb/tools/debugserver/source/MacOSX/DarwinLog/DarwinLogCollector.cpp
@@ -46,10 +46,10 @@ static os_activity_stream_set_event_handler_t
     s_os_activity_stream_set_event_handler;
 
 bool LookupSPICalls() {
-  static llvm::once_flag s_once_flag;
+  static std::once_flag s_once_flag;
   static bool s_has_spi;
 
-  llvm::call_once(s_once_flag, [] {
+  std::call_once(s_once_flag, [] {
     dlopen ("/System/Library/PrivateFrameworks/LoggingSupport.framework/LoggingSupport", RTLD_NOW);
     s_os_activity_stream_for_pid = (os_activity_stream_for_pid_t)dlsym(
         RTLD_DEFAULT, "os_activity_stream_for_pid");