diff -up dovecot-2.3.0.1/src/auth/mycrypt.c.libxcrypt dovecot-2.3.0.1/src/auth/mycrypt.c
--- dovecot-2.3.0.1/src/auth/mycrypt.c.libxcrypt       2018-02-28 15:28:58.000000000 +0100
+++ dovecot-2.3.0.1/src/auth/mycrypt.c 2018-03-27 10:57:38.447769201 +0200
@@ -14,6 +14,7 @@
 #  define _XPG6 /* Some Solaris versions require this, some break with this */
 #endif
 #include <unistd.h>
+#include <crypt.h>
 
 #include "mycrypt.h"