diff --git a/software/libnet/microudp.c b/software/libnet/microudp.c
index a96da8e9d..fce73819b 100644
--- a/software/libnet/microudp.c
+++ b/software/libnet/microudp.c
@@ -444,6 +444,7 @@ void ethreset(void)
 	busy_wait(2);
 }
 
+#ifdef CSR_ETHPHY_MODE_ADDR
 void ethmode(void)
 {
 	ethphy_clock_counter_reset_write(1);
@@ -465,6 +466,7 @@ void ethmode(void)
 
 	ethphy_clock_counter_reset_write(1);
 }
+#endif
 
 #endif