diff --git a/include/minix/config.h b/include/minix/config.h
index 35036b934..360343158 100644
--- a/include/minix/config.h
+++ b/include/minix/config.h
@@ -50,7 +50,7 @@
  * system can handle.
  */
 #define NR_CONS            4	/* # system consoles (1 to 8) */
-#define	NR_RS_LINES	   4	/* # rs232 terminals (0 to 4) */
+#define	NR_RS_LINES	   4	/* # rs232 terminals (0 to 3) */
 #define	NR_PTYS		   32	/* # pseudo terminals (0 to 64) */
 
 /* This feature enable the counting of system calls in PM and FS */