diff --git a/llvm/include/llvm/Support/Threading.h b/llvm/include/llvm/Support/Threading.h
index ba6c531ab4db2..13d21b0f3ea11 100644
--- a/llvm/include/llvm/Support/Threading.h
+++ b/llvm/include/llvm/Support/Threading.h
@@ -18,8 +18,8 @@
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Config/llvm-config.h" // for LLVM_ON_UNIX
 #include "llvm/Support/Compiler.h"
-#include <ciso646> // So we can check the C++ standard lib macros.
 #include <optional>
+#include <version>
 
 #if defined(_MSC_VER)
 // MSVC's call_once implementation worked since VS 2015, which is the minimum
diff --git a/llvm/lib/DebugInfo/GSYM/LookupResult.cpp b/llvm/lib/DebugInfo/GSYM/LookupResult.cpp
index 00a5b1bbfaa5f..0a09feefbd750 100644
--- a/llvm/lib/DebugInfo/GSYM/LookupResult.cpp
+++ b/llvm/lib/DebugInfo/GSYM/LookupResult.cpp
@@ -12,7 +12,6 @@
 #include "llvm/Support/Format.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
-#include <ciso646>
 
 using namespace llvm;
 using namespace gsym;