diff --git a/doc/reference.md b/doc/reference.md
index 24cfaa58b..a4ab39761 100644
--- a/doc/reference.md
+++ b/doc/reference.md
@@ -76,6 +76,8 @@ more than 20 milliseconds is not recommended.
 
 `Serial1` uses UART1, TX pin is GPIO2. UART1 can not be used to receive data because normally it's RX pin is occupied for flash chip connection. To use `Serial1`, call `Serial1.begin(baudrate)`.
 
+If `Serial1` is not used and `Serial` is not swapped - TX for UART0 can be mapped to GPIO2 instead by calling `Serial.set_tx(2)` after `Serial.begin` or directly with `Serial.begin(baud, config, mode, 2)`.
+
 By default the diagnostic output from WiFi libraries is disabled when you call `Serial.begin`. To enable debug output again, call `Serial.setDebugOutput(true)`. To redirect debug output to `Serial1` instead, call `Serial1.setDebugOutput(true)`.
 
 You also need to use `Serial.setDebugOutput(true)` to enable output from `printf()` function.