--- AltairZ80/i86_decode.c.orig	Thu Feb 18 15:20:53 2021
+++ AltairZ80/i86_decode.c	Thu Feb 18 15:21:15 2021
@@ -46,6 +46,8 @@
 extern uint32 sim_brk_summ;
 extern UNIT cpu_unit;
 
+volatile int intr;
+
 void i86_intr_raise(PC_ENV *m,uint8 intrnum);
 void cpu8086reset(void);
 t_stat sim_instr_8086(void);