1 files changed, 5 insertions, 1 deletions
diff --git a/newlib/libc/posix/_isatty.c b/newlib/libc/posix/_isatty.c
index 7260211ef..7d6ccae7c 100644
--- a/newlib/libc/posix/_isatty.c
+++ b/newlib/libc/posix/_isatty.c
@@ -3,15 +3,19 @@
 /* Dumb implementation so programs will at least run.  */
 
 #include <sys/stat.h>
+#include <errno.h>
 
 int
 _DEFUN(_isatty, (fd), int fd)
 {
   struct stat buf;
 
-  if (fstat (fd, &buf) < 0)
+  if (fstat (fd, &buf) < 0) {
+    errno = EBADF;
     return 0;
+  }
   if (S_ISCHR (buf.st_mode))
     return 1;
+  errno = ENOTTY;
   return 0;
 }