diff --git a/README.md b/README.md
index 572b4a56..69cbb8f0 100644
--- a/README.md
+++ b/README.md
@@ -37,6 +37,7 @@ boards and shields, including:
  - TI CC3000 WiFi - [library](https://github.com/sparkfun/SFE_CC3000_Library)
  - Intel Galileo/Edison
  - ESP8266
+ - ESP32
 
 The library cannot currently be used with hardware based on the ENC28J60 chip –
 such as the Nanode or the Nuelectronics Ethernet Shield. For those, there is an
diff --git a/src/PubSubClient.h b/src/PubSubClient.h
index 0d9c4f60..2fd6f1d6 100755
--- a/src/PubSubClient.h
+++ b/src/PubSubClient.h
@@ -76,7 +76,7 @@
 // Maximum size of fixed header and variable length size header
 #define MQTT_MAX_HEADER_SIZE 5
 
-#ifdef ESP8266
+#if defined(ESP8266) || defined(ESP32)
 #include <functional>
 #define MQTT_CALLBACK_SIGNATURE std::function<void(char*, uint8_t*, unsigned int)> callback
 #else