1 files changed, 1 insertions, 1 deletions
diff --git a/libio/bug-ungetc4.c b/libio/bug-ungetc4.c
index 82019b6d8e..0f530efecf 100644
--- a/libio/bug-ungetc4.c
+++ b/libio/bug-ungetc4.c
@@ -38,7 +38,7 @@ do_prepare (void)
       printf ("cannot create temporary file: %m\n");
       exit (1);
     }
-  write (fd, pattern, sizeof (pattern));
+  write (fd, pattern, sizeof (pattern) - 1);
   close (fd);
 }