diff -uNr usr.orig/include/pty.h usr/include/pty.h
--- usr.orig/include/pty.h	2019-06-23 18:06:46.017740027 +0000
+++ ./usr/include/pty.h	2019-06-23 18:08:43.889397155 +0000
@@ -40,29 +40,8 @@

 __BEGIN_DECLS

-/**
- * [openpty(3)](http://man7.org/linux/man-pages/man3/openpty.3.html) finds
- * a free pseudoterminal and configures it with the given terminal and window
- * size settings.
- *
- * Returns 0 on success and returns -1 and sets `errno` on failure.
- *
- * Available since API level 23.
- */
-
-#if __ANDROID_API__ >= 23
-int openpty(int* _Nonnull __master_fd, int* _Nonnull __slave_fd, char* _Nullable __slave_name, const struct termios* _Nullable __termios_ptr, const struct winsize* _Nullable __winsize_ptr) __INTRODUCED_IN(23);
-
-/**
- * [forkpty(3)](http://man7.org/linux/man-pages/man3/forkpty.3.html) creates
- * a new process connected to a pseudoterminal from openpty().
- *
- * Returns 0 on success and returns -1 and sets `errno` on failure.
- *
- * Available since API level 23.
- */
-int forkpty(int* _Nonnull __master_fd, char* _Nullable __slave_name, const struct termios* _Nullable __termios_ptr, const struct winsize* _Nullable __winsize_ptr) __INTRODUCED_IN(23);
-#endif /* __ANDROID_API__ >= 23 */
-
+/* In Termux these are implemented in the libutil package to support android-21. */
+int openpty(int* __master_fd, int* __slave_fd, char* __slave_name, const struct termios* __termios_ptr, const struct winsize* __winsize_ptr);
+int forkpty(int* __master_fd, char* __slave_name, const struct termios* __termios_ptr, const struct winsize* __winsize_ptr);

 __END_DECLS