diff --git a/prefab/packet_parsers/dhcp.c b/prefab/packet_parsers/dhcp.c
index eade4d1..1e61d0b 100644
--- a/prefab/packet_parsers/dhcp.c
+++ b/prefab/packet_parsers/dhcp.c
@@ -16,7 +16,7 @@ static struct {
     cbd desc;
     uint32_t tranId;
     EthInterface *intf;
-    ETHLIB_OS_SEM_TYPE procSem;
+    ETHLIB_OS_MTX_TYPE procMtx;
 } s;
 
 static const uint8_t DHCP_MAGIC_COOKIE[] = {99, 130, 83, 99};
@@ -249,7 +249,7 @@ void dhcp_request(ip4_addr reqAddr, ip4_addr dhcpServerAddr) {
 }
 
 static void dhcp_process(DhcpProps *props, DhcpOption *opts) {
-    ETHLIB_OS_SEM_WAIT(&s.procSem); // LOCK!
+    ETHLIB_OS_MTX_LOCK(&s.procMtx); // LOCK!
 
     switch (s.state) {
         case DHCP_INIT:
@@ -313,7 +313,7 @@ static void dhcp_process(DhcpProps *props, DhcpOption *opts) {
             break;
     }
 
-    ETHLIB_OS_SEM_POST(&s.procSem); // RELEASE!
+    ETHLIB_OS_MTX_UNLOCK(&s.procMtx); // RELEASE!
 }
 
 static int dhcp_resp_cb(const Pckt *pckt, PcktSieveLayerTag tag) {
@@ -334,8 +334,7 @@ void dhcp_start() {
 }
 
 void dhcp_initiate(EthInterface *intf) {
-    ETHLIB_OS_SEM_CREATE(&s.procSem);
-    ETHLIB_OS_SEM_POST(&s.procSem);
+    ETHLIB_OS_MTX_CREATE(&s.procMtx);
     s.state = DHCP_INIT;
     s.buf = dynmem_alloc(DHCP_MIN_PACKET_SIZE);
     s.desc = udp_new_connblock(intf, IPv4_ANY_ADDR, DHCP_CLIENT_PORT, dhcp_resp_cb);