diff --git a/TESTS/netsocket/udp/udpsocket_sendto_invalid.cpp b/TESTS/netsocket/udp/udpsocket_sendto_invalid.cpp
index 6b16c28a15..a911c8a533 100644
--- a/TESTS/netsocket/udp/udpsocket_sendto_invalid.cpp
+++ b/TESTS/netsocket/udp/udpsocket_sendto_invalid.cpp
@@ -32,7 +32,12 @@ void UDPSOCKET_SENDTO_INVALID()
     TEST_ASSERT(sock.sendto(NULL, 9, NULL, 0) < 0);
     TEST_ASSERT(sock.sendto("", 9, NULL, 0) < 0);
     TEST_ASSERT(sock.sendto("", 0, NULL, 0) < 0);
-    TEST_ASSERT_EQUAL(0, sock.sendto(MBED_CONF_APP_ECHO_SERVER_ADDR, 9, NULL, 0));
+
+    nsapi_error_t result = sock.sendto(MBED_CONF_APP_ECHO_SERVER_ADDR, 9, NULL, 0);
+    if (result != NSAPI_ERROR_UNSUPPORTED) {
+        TEST_ASSERT_EQUAL(0, result);
+    }
+
     TEST_ASSERT_EQUAL(5, sock.sendto(MBED_CONF_APP_ECHO_SERVER_ADDR, 9, "hello", 5));
 
     TEST_ASSERT_EQUAL(NSAPI_ERROR_OK, sock.close());
diff --git a/components/wifi/esp8266-driver/ESP8266Interface.cpp b/components/wifi/esp8266-driver/ESP8266Interface.cpp
index 08c9100587..eea53d71a4 100644
--- a/components/wifi/esp8266-driver/ESP8266Interface.cpp
+++ b/components/wifi/esp8266-driver/ESP8266Interface.cpp
@@ -568,6 +568,11 @@ int ESP8266Interface::socket_send(void *handle, const void *data, unsigned size)
         return NSAPI_ERROR_NO_SOCKET;
     }
 
+    if (!size) {
+        // Firmware limitation
+        return socket->proto == NSAPI_TCP ? 0 : NSAPI_ERROR_UNSUPPORTED;
+    }
+
     unsigned long int sendStartTime = rtos::Kernel::get_ms_count();
     do {
         status = _esp.send(socket->id, data, size);