--- a/sys/ddb/db_input.c
+++ b/sys/ddb/db_input.c
@@ -247,7 +247,8 @@
 		db_putnchars(BLANK, db_le - db_lbuf_start);
 		db_putnchars(BACKUP, db_le - db_lbuf_start);
 		db_le = index(db_lbuf_start, '\0');
-		if (db_le[-1] == '\r' || db_le[-1] == '\n')
+		if (db_le > db_lbuf_start &&
+		    (db_le[-1] == '\r' || db_le[-1] == '\n'))
 		    *--db_le = '\0';
 		db_lc = db_le;
 		goto redraw;