diff --git a/src/cmd/internal/gc/go.go b/src/cmd/internal/gc/go.go
index 5803f39..25ada55 100644
--- a/src/cmd/internal/gc/go.go
+++ b/src/cmd/internal/gc/go.go
@@ -769,6 +769,7 @@
 	REGRETURN    int // AX
 	REGMIN       int
 	REGMAX       int
+	REGZERO      int // architectural zero register, if available
 	FREGMIN      int
 	FREGMAX      int
 	MAXWIDTH     int64