diff --git a/sys/dev/tpm/tpm20.c b/sys/dev/tpm/tpm20.c
--- a/sys/dev/tpm/tpm20.c
+++ b/sys/dev/tpm/tpm20.c
@@ -73,7 +73,6 @@
 
 	sc = (struct tpm_sc *)dev->si_drv1;
 
-	callout_stop(&sc->discard_buffer_callout);
 	sx_xlock(&sc->dev_lock);
 	if (sc->owner_tid != uio->uio_td->td_tid) {
 		sx_xunlock(&sc->dev_lock);