diff --git a/sys/arm64/arm64/machdep.c b/sys/arm64/arm64/machdep.c
--- a/sys/arm64/arm64/machdep.c
+++ b/sys/arm64/arm64/machdep.c
@@ -380,6 +380,7 @@
 #endif
 	thread0.td_pcb = (struct pcb *)(thread0.td_kstack +
 	    thread0.td_kstack_pages * PAGE_SIZE) - 1;
+	thread0.td_pcb->pcb_flags = 0;
 	thread0.td_pcb->pcb_fpflags = 0;
 	thread0.td_pcb->pcb_fpusaved = &thread0.td_pcb->pcb_fpustate;
 	thread0.td_pcb->pcb_vfpcpu = UINT_MAX;