diff --git a/cde/programs/dtdocbook/instant/main.c b/cde/programs/dtdocbook/instant/main.c
index 5f067975c..7cd0f95a9 100644
--- a/cde/programs/dtdocbook/instant/main.c
+++ b/cde/programs/dtdocbook/instant/main.c
@@ -78,6 +78,7 @@ static char *CopyRt =
 #include <dirent.h>
 #include <time.h>
 #include <fcntl.h>
+#include <unistd.h>
 #include <locale.h>
 #include "LocaleXlate.h"
 #include "XlationSvc.h"