diff --git a/src/cmd/5g/gg.h b/src/cmd/5g/gg.h
index ce4575be959..78e6833b2ae 100644
--- a/src/cmd/5g/gg.h
+++ b/src/cmd/5g/gg.h
@@ -52,7 +52,7 @@ struct	Prog
 
 EXTERN	Biobuf*	bout;
 EXTERN	int32	dynloc;
-EXTERN	uchar	reg[REGALLOC_FMAX];
+EXTERN	uchar	reg[REGALLOC_FMAX+1];
 EXTERN	int32	pcloc;		// instruction counter
 EXTERN	Strlit	emptystring;
 extern	char*	anames[];