diff --git a/riscv/aia.c b/riscv/aia.c
index fe9399a..21d9704 100644
--- a/riscv/aia.c
+++ b/riscv/aia.c
@@ -164,7 +164,7 @@
 	ret = ioctl(aia_fd, KVM_SET_DEVICE_ATTR, &aia_nr_sources_attr);
 	if (ret)
 		return ret;
-	aia_hart_bits = fls_long(kvm->nrcpus);
+	aia_hart_bits = fls_long(kvm->nrcpus - 1);
 	ret = ioctl(aia_fd, KVM_SET_DEVICE_ATTR, &aia_hart_bits_attr);
 	if (ret)
 		return ret;