diff --git a/sys/arm64/arm64/trap.c b/sys/arm64/arm64/trap.c
index 1db574273bd0..ea932edca8f6 100644
--- a/sys/arm64/arm64/trap.c
+++ b/sys/arm64/arm64/trap.c
@@ -313,13 +313,11 @@ do_el1h_sync(struct trapframe *frame)
  * instruction results in an exception with an unknown reason.
  */
 static void
-el0_excp_unknown(struct trapframe *frame)
+el0_excp_unknown(struct trapframe *frame, uint64_t far)
 {
 	struct thread *td;
-	uint64_t far;
 
 	td = curthread;
-	far = READ_SPECIALREG(far_el1);
 	call_trapsignal(td, SIGILL, ILL_ILLTRP, (void *)far);
 	userret(td, frame);
 }
@@ -342,6 +340,7 @@ do_el0_sync(struct trapframe *frame)
 	esr = READ_SPECIALREG(esr_el1);
 	exception = ESR_ELx_EXCEPTION(esr);
 	switch (exception) {
+	case EXCP_UNKNOWN:
 	case EXCP_INSN_ABORT_L:
 	case EXCP_DATA_ABORT_L:
 	case EXCP_DATA_ABORT:
@@ -371,7 +370,7 @@ do_el0_sync(struct trapframe *frame)
 		data_abort(frame, esr, far, 1);
 		break;
 	case EXCP_UNKNOWN:
-		el0_excp_unknown(frame);
+		el0_excp_unknown(frame, far);
 		break;
 	case EXCP_SP_ALIGN:
 		call_trapsignal(td, SIGBUS, BUS_ADRALN, (void *)frame->tf_sp);