--- screen-4.0.3.orig/osdef.h.in
+++ screen-4.0.3/osdef.h.in
@@ -107,6 +107,7 @@
 extern char *tgoto __P((char *, int, int));
 
 #ifdef POSIX
+#include <string.h>
 extern int   setsid __P((void));
 extern int   setpgid __P((int, int));
 extern int   tcsetpgrp __P((int, int));