Index: lib/Format/Format.cpp
===================================================================
--- lib/Format/Format.cpp
+++ lib/Format/Format.cpp
@@ -1917,7 +1917,10 @@
   // Look for .clang-format/_clang-format file in the file's parent directories.
   SmallString<128> UnsuitableConfigFiles;
   SmallString<128> Path(FileName);
-  llvm::sys::fs::make_absolute(Path);
+  std::error_code EC = FS->makeAbsolute(Path);
+  assert(!EC);
+  (void)EC;
+
   for (StringRef Directory = Path; !Directory.empty();
        Directory = llvm::sys::path::parent_path(Directory)) {
 
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -10907,10 +10907,6 @@
             format("auto a = unique_ptr < Foo < Bar>[10]> ;", Spaces));
 }
 
-// Since this test case uses UNIX-style file path. We disable it for MS
-// compiler.
-#if !defined(_MSC_VER) && !defined(__MINGW32__)
-
 TEST(FormatStyle, GetStyleOfFile) {
   vfs::InMemoryFileSystem FS;
   // Test 1: format file in the same directory.
@@ -10938,8 +10934,6 @@
   ASSERT_EQ(Style3, getGoogleStyle());
 }
 
-#endif // _MSC_VER
-
 TEST_F(ReplacementTest, FormatCodeAfterReplacements) {
   // Column limit is 20.
   std::string Code = "Type *a =\n"