diff --git a/src/core/tcp.c b/src/core/tcp.c
index c5c6d297..95c7b011 100644
--- a/src/core/tcp.c
+++ b/src/core/tcp.c
@@ -873,14 +873,16 @@ tcp_new_port(void)
   struct tcp_pcb *pcb;
 
 again:
-  if (tcp_port++ == TCP_LOCAL_PORT_RANGE_END) {
+  tcp_port++;
+  if (tcp_port == TCP_LOCAL_PORT_RANGE_END) {
     tcp_port = TCP_LOCAL_PORT_RANGE_START;
   }
   /* Check all PCB lists. */
   for (i = 0; i < NUM_TCP_PCB_LISTS; i++) {
     for (pcb = *tcp_pcb_lists[i]; pcb != NULL; pcb = pcb->next) {
       if (pcb->local_port == tcp_port) {
-        if (++n > (TCP_LOCAL_PORT_RANGE_END - TCP_LOCAL_PORT_RANGE_START)) {
+        n++;
+        if (n > (TCP_LOCAL_PORT_RANGE_END - TCP_LOCAL_PORT_RANGE_START)) {
           return 0;
         }
         goto again;