diff --git a/cores/esp8266/HardwareSerial.cpp b/cores/esp8266/HardwareSerial.cpp
index 194a0553e..5f7ea141c 100644
--- a/cores/esp8266/HardwareSerial.cpp
+++ b/cores/esp8266/HardwareSerial.cpp
@@ -133,7 +133,7 @@ unsigned long HardwareSerial::testBaudrate()
 unsigned long HardwareSerial::detectBaudrate(time_t timeoutMillis)
 {
     esp8266::polledTimeout::oneShotFastMs timeOut(timeoutMillis);
-    unsigned long detectedBaudrate;
+    unsigned long detectedBaudrate = 0;
     while (!timeOut) {
         if ((detectedBaudrate = testBaudrate())) {
           break;