diff --git a/tparam.c b/tparam.c
index 5a9809a..09ef456 100644
--- a/tparam.c
+++ b/tparam.c
@@ -40,6 +40,10 @@ char *realloc ();
#endif /* not emacs */
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
#ifndef NULL
#define NULL (char *) 0
#endif
