diff --git a/libbb/pw_encrypt.c b/libbb/pw_encrypt.c
index 1edf4b6f0..86455cd0d 100644
--- a/libbb/pw_encrypt.c
+++ b/libbb/pw_encrypt.c
@@ -6,6 +6,7 @@
  *
  * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
+#include <crypt.h>
 #include "libbb.h"
 
 /* static const uint8_t ascii64[] ALIGN1 =