diff --git a/sim_timer.c b/sim_timer.c
index e5e0a494..38a2def4 100644
--- a/sim_timer.c
+++ b/sim_timer.c
@@ -3457,9 +3457,9 @@ while (*cmd)
      exdep_cmd (EX_D, *(cmd++));
 sim_switches = saved_switches;
 sim_cancel (&SIM_INTERNAL_UNIT);
-sim_activate (&precalib_unit, sim_precalibrate_ips);
 start = sim_os_msec();
 do {
+    sim_activate (&precalib_unit, sim_precalibrate_ips);
     sim_instr();
     end = sim_os_msec();
     } while ((end - start) < SIM_PRE_CALIBRATE_MIN_MS);