diff --git a/src/cmd/8g/peep.c b/src/cmd/8g/peep.c
index 35129a7c46..91a91d20db 100644
--- a/src/cmd/8g/peep.c
+++ b/src/cmd/8g/peep.c
@@ -636,9 +636,9 @@ copyu(Prog *p, Adr *v, Adr *s)
 static int
 copyas(Adr *a, Adr *v)
 {
-	if(D_AL <= a->type && a->type <= D_R15B)
+	if(D_AL <= a->type && a->type <= D_BL)
 		fatal("use of byte register");
-	if(D_AL <= v->type && v->type <= D_R15B)
+	if(D_AL <= v->type && v->type <= D_BL)
 		fatal("use of byte register");
 
 	if(a->type != v->type)