diff --git a/libraries/SITL/SIM_ADSB.cpp b/libraries/SITL/SIM_ADSB.cpp
index 256a171921..9e4317251a 100644
--- a/libraries/SITL/SIM_ADSB.cpp
+++ b/libraries/SITL/SIM_ADSB.cpp
@@ -117,8 +117,8 @@ void ADSB::send_report(void)
         // threading issue with non-blocking sockets and the initial wait on uartA
         return;
     }
-    if (!mavlink.connected && mav_socket.connect(target_address, target_port)) {
-        ::printf("ADSB connected to %s:%u\n", target_address, (unsigned)target_port);
+    if (!mavlink.connected && mav_socket.connect(target_address, target_port_base + 10 * instance)) {
+        ::printf("ADSB connected to %s:%u\n", target_address, (unsigned)target_port_base + 10 * instance);
         mavlink.connected = true;
     }
     if (!mavlink.connected) {
diff --git a/libraries/SITL/SIM_ADSB.h b/libraries/SITL/SIM_ADSB.h
index 4a8156fdc1..c7ee15b270 100644
--- a/libraries/SITL/SIM_ADSB.h
+++ b/libraries/SITL/SIM_ADSB.h
@@ -51,12 +51,14 @@ private:
         
 class ADSB {
 public:
-    ADSB(const struct sitl_fdm &_fdm, const Location& _home) : home(_home) {};
+    ADSB(const struct sitl_fdm &_fdm, const Location& _home, const uint8_t _instance) : home(_home), instance(_instance) {};
     void update(void);
 
 private:
     const char *target_address = "127.0.0.1";
-    const uint16_t target_port = 5762;
+    const uint16_t target_port_base = 5762;
+
+    const uint8_t instance = 0;
 
     const Location& home;
     uint8_t num_vehicles = 0;