diff --git a/llvm/lib/Support/Errno.cpp b/llvm/lib/Support/Errno.cpp
--- a/llvm/lib/Support/Errno.cpp
+++ b/llvm/lib/Support/Errno.cpp
@@ -18,6 +18,10 @@
 #include <errno.h>
 #endif
 
+#if !HAVE_STRERROR_R && !HAVE_DECL_STRERROR_S && !HAVE_STRERROR
+#include "llvm/Support/raw_ostream.h"
+#endif
+
 //===----------------------------------------------------------------------===//
 //=== WARNING: Implementation here must contain only TRULY operating system
 //===          independent code.