diff --git a/libraries/libldap/cyrus.c b/libraries/libldap/cyrus.c
index d687c4cec6..1816d8d7c3 100644
--- a/libraries/libldap/cyrus.c
+++ b/libraries/libldap/cyrus.c
@@ -14,6 +14,7 @@
 #include <ac/time.h>
 #include <ac/errno.h>
 #include <ac/ctype.h>
+#include <ac/unistd.h>
 
 #include "ldap-int.h"