diff -uNr busybox-1.31.1/libbb/pw_encrypt.c busybox-1.31.1.mod/libbb/pw_encrypt.c
--- busybox-1.31.1/libbb/pw_encrypt.c	2019-06-10 13:50:53.000000000 +0300
+++ busybox-1.31.1.mod/libbb/pw_encrypt.c	2019-11-11 22:16:44.990795793 +0200
@@ -6,7 +6,10 @@
  *
  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
-#include <crypt.h>
+#if !ENABLE_USE_BB_CRYPT
+# include <crypt.h>
+#endif
+
 #include "libbb.h"
 
 /* static const uint8_t ascii64[] ALIGN1 =