1 files changed, 8 insertions, 1 deletions
diff --git a/newlib/libc/stdio/fileno.c b/newlib/libc/stdio/fileno.c
index 818f1a1ca..be8f3d66a 100644
--- a/newlib/libc/stdio/fileno.c
+++ b/newlib/libc/stdio/fileno.c
@@ -47,6 +47,7 @@ Supporting OS subroutines required: none.
 
 #include <_ansi.h>
 #include <stdio.h>
+#include <errno.h>
 #include "local.h"
 
 int
@@ -56,7 +57,13 @@ _DEFUN(fileno, (f),
   int result;
   CHECK_INIT (_REENT, f);
   _newlib_flockfile_start (f);
-  result = __sfileno (f);
+  if (f->_flags)
+    result = __sfileno (f);
+  else
+    {
+      result = -1;
+      _REENT->_errno = EBADF;
+    }
   _newlib_flockfile_end (f);
   return result;
 }