diff --git a/sys/powerpc/aim/machdep.c b/sys/powerpc/aim/machdep.c
index fb83e3af4798..4e8909fc1563 100644
--- a/sys/powerpc/aim/machdep.c
+++ b/sys/powerpc/aim/machdep.c
@@ -505,6 +505,7 @@ powerpc_init(u_int startkernel, u_int endkernel, u_int basekernel, void *mdp)
 	thread0.td_pcb = (struct pcb *)
 	    ((thread0.td_kstack + thread0.td_kstack_pages * PAGE_SIZE -
 	    sizeof(struct pcb)) & ~15);
+	bzero((void *)thread0.td_pcb, sizeof(struct pcb));
 	pc->pc_curpcb = thread0.td_pcb;
 
 	/* Initialise the message buffer. */