diff --git a/cores/esp8266/uart.cpp b/cores/esp8266/uart.cpp
index 802072d438..020d4a39e7 100644
--- a/cores/esp8266/uart.cpp
+++ b/cores/esp8266/uart.cpp
@@ -537,7 +537,7 @@ uart_write(uart_t* uart, const char* buf, size_t size)
 
     if(gdbstub_has_uart_isr_control() && uart->uart_nr == UART0) {
         gdbstub_write(buf, size);
-        return 0;
+        return size;
     }
 
     size_t ret = size;