diff --git a/repos/os/src/drivers/nic/gem/marvell_phy.h b/repos/os/src/drivers/nic/gem/marvell_phy.h
index c1bb13b7ab..202214a5ae 100644
--- a/repos/os/src/drivers/nic/gem/marvell_phy.h
+++ b/repos/os/src/drivers/nic/gem/marvell_phy.h
@@ -163,7 +163,7 @@ namespace Genode
 
 			Timer::Connection _timer;
 			Phyio& _phyio;
-			uint8_t _phyaddr;
+			int8_t _phyaddr;
 			bool _link_up;
 			Eth_speed _eth_speed;