diff --git a/src/chardev.c b/src/chardev.c
index 544091a..33a3136 100644
--- a/src/chardev.c
+++ b/src/chardev.c
@@ -46,6 +46,7 @@ static char *id = "$Id: chardev.c,v 1.2 1999/01/03 02:06:50 sybalsky Exp $ Copyr
 #include <string.h>
 #endif /* DOS */
 
+#include <unistd.h>
 #include <setjmp.h>
 #include <signal.h>
 #include <errno.h>
diff --git a/src/ldeboot.c b/src/ldeboot.c
index f583964..50ce7fb 100644
--- a/src/ldeboot.c
+++ b/src/ldeboot.c
@@ -38,6 +38,7 @@ static char *id = "$Id: ldeboot.c,v 1.3 1999/01/03 02:07:13 sybalsky Exp $ Copyr
 #include <errno.h>
 #include <string.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 #ifdef XWINDOW
 #ifndef SYSVONLY
diff --git a/src/setsout.c b/src/setsout.c
index 8b47c52..0937cdf 100644
--- a/src/setsout.c
+++ b/src/setsout.c
@@ -27,6 +27,7 @@ static char *id = "$Id: setsout.c,v 1.3 1999/05/31 23:35:41 sybalsky Exp $ Copyr
 /************************************************************************/
 
 #include <stdio.h>
+#include <unistd.h>
 #include <sys/file.h>
 #include <sys/types.h>
 #include <sys/stat.h>
diff --git a/src/tstsout.c b/src/tstsout.c
index f3dc308..594c25d 100644
--- a/src/tstsout.c
+++ b/src/tstsout.c
@@ -20,6 +20,7 @@ static char *id = "$Id: tstsout.c,v 1.3 1999/05/31 23:35:44 sybalsky Exp $ Copyr
 #include "version.h"
 
 #include <stdio.h>
+#include <unistd.h>
 #include <sys/file.h>
 #include <sys/types.h>
 #include <sys/stat.h>