diff --git a/lib/Support/Errno.cpp b/lib/Support/Errno.cpp
index 1eefa3e6f8d..3ba2a1277d0 100644
--- a/lib/Support/Errno.cpp
+++ b/lib/Support/Errno.cpp
@@ -35,12 +35,14 @@ std::string StrError() {
 #endif  // HAVE_ERRNO_H
 
 std::string StrError(int errnum) {
-  const int MaxErrStrLen = 2000;
-  char buffer[MaxErrStrLen];
-  buffer[0] = '\0';
   std::string str;
   if (errnum == 0)
     return str;
+#if defined(HAVE_STRERROR_R) || HAVE_DECL_STRERROR_S
+  const int MaxErrStrLen = 2000;
+  char buffer[MaxErrStrLen];
+  buffer[0] = '\0';
+#endif  
 
 #ifdef HAVE_STRERROR_R
   // strerror_r is thread-safe.