diff --git a/src/cmd/ed.c b/src/cmd/ed.c
index 788b35be..90bb6315 100644
--- a/src/cmd/ed.c
+++ b/src/cmd/ed.c
@@ -1050,7 +1050,7 @@ putline(void)
 		}
 	}
 	nl = tline;
-	tline += ((lp-linebuf) + 03) & 077776;
+	tline += ((lp-linebuf) + 03) & (NBLK-1);
 	return nl;
 }