diff --git a/sys/dev/mrsas/mrsas.c b/sys/dev/mrsas/mrsas.c
--- a/sys/dev/mrsas/mrsas.c
+++ b/sys/dev/mrsas/mrsas.c
@@ -1732,11 +1732,13 @@
 						data_length = r1_cmd->io_request->DataLength;
 						sense = r1_cmd->sense;
 					}
+					mtx_lock(&sc->sim_lock);
 					r1_cmd->ccb_ptr = NULL;
 					if (r1_cmd->callout_owner) {
 						callout_stop(&r1_cmd->cm_callout);
 						r1_cmd->callout_owner  = false;
 					}
+					mtx_unlock(&sc->sim_lock);
 					mrsas_release_mpt_cmd(r1_cmd);
 					mrsas_atomic_dec(&sc->fw_outstanding);
 					mrsas_map_mpt_cmd_status(cmd_mpt, cmd_mpt->ccb_ptr, status,