diff --git a/dhcp.c b/dhcp.c
index c7a359c..b9cb7df 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -413,7 +413,7 @@ static void init_packet(struct dhcpmsg *packet, uint8_t type)
 
 ssize_t send_discover(struct client_state_t *cs)
 {
-    cs->xid = nk_random_u32(&cs->rnd_state);
+    advance_xid(cs);
     struct dhcpmsg packet = {.xid = cs->xid};
     init_packet(&packet, DHCPDISCOVER);
     if (cs->clientAddr)
diff --git a/ndhc.h b/ndhc.h
index 3b3571d..917cf5c 100644
--- a/ndhc.h
+++ b/ndhc.h
@@ -86,5 +86,12 @@ void signal_exit(int status);
 int get_clientid_string(const char *str, size_t slen);
 void print_version(void);
 
+static inline void advance_xid(struct client_state_t *cs) {
+    uint32_t o = cs->xid;
+    do {
+        cs->xid = nk_random_u32(&cs->rnd_state);
+    } while (cs->xid == o);
+}
+
 #endif
 
diff --git a/state.c b/state.c
index 474ff42..9e7ffa0 100644
--- a/state.c
+++ b/state.c
@@ -53,7 +53,7 @@ static int delay_timeout(struct client_state_t *cs, size_t numpackets)
 static void reinit_shared_deconfig(struct client_state_t *cs)
 {
     nk_random_init(&cs->rnd_state);
-    cs->xid = nk_random_u32(&cs->rnd_state);
+    advance_xid(cs);
     cs->clientAddr = 0;
     cs->num_dhcp_requests = 0;
     cs->num_dhcp_renews = 0;
@@ -224,7 +224,7 @@ static int extend_packet(struct client_state_t *cs,
                       clibuf, sizeof clibuf);
             log_line("%s: Server is now offering IP %s.  Validating...",
                      client_config.interface, clibuf);
-            cs->xid = nk_random_u32(&cs->rnd_state);
+            advance_xid(cs);
             return ANP_CHECK_IP;
         } else {
             log_line("%s: Lease refreshed to %u seconds.",
@@ -233,7 +233,7 @@ static int extend_packet(struct client_state_t *cs,
                 log_line("%s: Failed to create ARP defense socket.",
                          client_config.interface);
             stop_dhcp_listen(cs);
-            cs->xid = nk_random_u32(&cs->rnd_state);
+            advance_xid(cs);
             return ANP_SUCCESS;
         }
     } else if (msgtype == DHCPNAK) {