diff --git a/llvm/include/llvm/Support/FileUtilities.h b/llvm/include/llvm/Support/FileUtilities.h
--- a/llvm/include/llvm/Support/FileUtilities.h
+++ b/llvm/include/llvm/Support/FileUtilities.h
@@ -14,6 +14,7 @@
 #ifndef LLVM_SUPPORT_FILEUTILITIES_H
 #define LLVM_SUPPORT_FILEUTILITIES_H
 
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -109,7 +110,7 @@
 
   llvm::Error
   writeFileAtomically(StringRef TempPathModel, StringRef FinalPath,
-                      std::function<llvm::Error(llvm::raw_ostream &)> Writer);
+                      llvm::function_ref<llvm::Error(llvm::raw_ostream &)> Writer);
 } // End llvm namespace
 
 #endif
diff --git a/llvm/lib/Support/FileUtilities.cpp b/llvm/lib/Support/FileUtilities.cpp
--- a/llvm/lib/Support/FileUtilities.cpp
+++ b/llvm/lib/Support/FileUtilities.cpp
@@ -296,7 +296,7 @@
 
 llvm::Error llvm::writeFileAtomically(
     StringRef TempPathModel, StringRef FinalPath,
-    std::function<llvm::Error(llvm::raw_ostream &)> Writer) {
+    llvm::function_ref<llvm::Error(llvm::raw_ostream &)> Writer) {
   SmallString<128> GeneratedUniqPath;
   int TempFD;
   if (sys::fs::createUniqueFile(TempPathModel.str(), TempFD,