diff --git a/Ethernet/socket.c b/Ethernet/socket.c
index 4f6ee50..45bf614 100644
--- a/Ethernet/socket.c
+++ b/Ethernet/socket.c
@@ -199,7 +199,7 @@ int8_t socket(uint8_t sn, uint8_t protocol, uint16_t port, uint8_t flag) {
     uint8_t taddr[16];
     uint16_t local_port = 0;
     CHECK_SOCKNUM();
-    switch (protocol & 0x0F) {
+    switch (protocol) {
 #ifdef IPV6_AVAILABLE
     case Sn_MR_TCP4 :
         getSIPR(taddr);