diff --git a/avr/modules/network/iface.asm b/avr/modules/network/iface.asm
index 06f9a20..b0174f9 100644
--- a/avr/modules/network/iface.asm
+++ b/avr/modules/network/iface.asm
@@ -188,9 +188,9 @@ NET_Interface_IncCounter16_end:
 
 NET_Interface_SetIfaceNumInBuffer:
   ldd r16, Y+NET_IFACE_OFFS_IFACENUM
-  andi r16, (NET_IFACE_BUFFER_IFACENUM1_BIT | NET_IFACE_BUFFER_IFACENUM0_BIT)
+  andi r16, (1<<NET_IFACE_BUFFER_IFACENUM1_BIT) | (1<<NET_IFACE_BUFFER_IFACENUM0_BIT)
   ld r17, X
-  andi r17, ~(NET_IFACE_BUFFER_IFACENUM1_BIT | NET_IFACE_BUFFER_IFACENUM0_BIT)
+  cbr r17, (1<<NET_IFACE_BUFFER_IFACENUM1_BIT) | (1<<NET_IFACE_BUFFER_IFACENUM0_BIT)
   or r17, r16
   st X, r17
   ret