diff --git a/sys/riscv/riscv/vm_machdep.c b/sys/riscv/riscv/vm_machdep.c
--- a/sys/riscv/riscv/vm_machdep.c
+++ b/sys/riscv/riscv/vm_machdep.c
@@ -179,6 +179,8 @@
 	tf->tf_sp = STACKALIGN((uintptr_t)stack->ss_sp + stack->ss_size);
 	tf->tf_sepc = (register_t)entry;
 	tf->tf_a[0] = (register_t)arg;
+	tf->tf_ra = 0;  /* Tell unwinders there is no return address. */
+	tf->tf_s[0] = 0;  /* Tell unwinders there is no stack frame above. */
 	return (0);
 }