diff --git a/unittests/Support/raw_pwrite_stream_test.cpp b/unittests/Support/raw_pwrite_stream_test.cpp
index 4e521a04728..a62f6bacb07 100644
--- a/unittests/Support/raw_pwrite_stream_test.cpp
+++ b/unittests/Support/raw_pwrite_stream_test.cpp
@@ -50,6 +50,7 @@ TEST(raw_pwrite_ostreamTest, TestFD) {
 #endif
 }
 
+#ifdef LLVM_ON_UNIX
 TEST(raw_pwrite_ostreamTest, TestDevNull) {
   int FD;
   sys::fs::openFileForWrite("/dev/null", FD, sys::fs::F_None);
@@ -59,4 +60,5 @@ TEST(raw_pwrite_ostreamTest, TestDevNull) {
   OS.pwrite(Test.data(), Test.size(), 0);
   OS.pwrite(Test.data(), Test.size(), 0);
 }
+#endif
 }