sys.check_interval=x -> sys.setcheckinterval(x)
diff --git a/Include/sysmodule.h b/Include/sysmodule.h
index 46d0070..1f1589a 100644
--- a/Include/sysmodule.h
+++ b/Include/sysmodule.h
@@ -36,6 +36,7 @@
 void initsys PROTO((void));
 
 extern DL_IMPORT object *sys_trace, *sys_profile;
+extern DL_IMPORT int sys_checkinterval;
 
 #ifdef __cplusplus
 }