diff --git a/repos/os/include/virtio/queue.h b/repos/os/include/virtio/queue.h
index d7253e205e..fc5e6b0b8f 100644
--- a/repos/os/include/virtio/queue.h
+++ b/repos/os/include/virtio/queue.h
@@ -423,7 +423,7 @@ class Virtio::Queue
 			 * Only the first descritor in the chain needs to be pushed to the available ring.
 			 */
 			_avail->ring[_avail->idx % _queue_size] = write_result.first_descriptor_idx;
-			_avail->idx += 1;
+			_avail->idx = _avail->idx + 1;
 			_avail->flags = Avail::Flags::NO_INTERRUPT;
 
 			return true;
diff --git a/repos/os/src/drivers/nic/include/drivers/nic/uplink_client_base.h b/repos/os/src/drivers/nic/include/drivers/nic/uplink_client_base.h
index 0d3df4ceb8..d760c8757b 100644
--- a/repos/os/src/drivers/nic/include/drivers/nic/uplink_client_base.h
+++ b/repos/os/src/drivers/nic/include/drivers/nic/uplink_client_base.h
@@ -32,8 +32,8 @@ class Genode::Uplink_client_base : Noncopyable
 
 		enum class Write_result { WRITE_SUCCEEDED, WRITE_FAILED };
 
-		enum { PKT_SIZE = Nic::Packet_allocator::DEFAULT_PACKET_SIZE };
-		enum { BUF_SIZE = Uplink::Session::QUEUE_SIZE * PKT_SIZE };
+		static constexpr size_t PKT_SIZE = Nic::Packet_allocator::DEFAULT_PACKET_SIZE;
+		static constexpr size_t BUF_SIZE = Uplink::Session::QUEUE_SIZE * PKT_SIZE;
 
 		Env                                &_env;
 		Allocator                          &_alloc;