diff --git a/src/PubSubClient.cpp b/src/PubSubClient.cpp
index 5c02339..3620057 100755
--- a/src/PubSubClient.cpp
+++ b/src/PubSubClient.cpp
@@ -570,7 +570,7 @@ PubSubClient& PubSubClient::setServer(const char * domain, uint16_t port) {
     return *this;
 }
 
-PubSubClient& PubSubClient::setCallback(void(*callback)(char*,uint8_t*,unsigned int)){
+PubSubClient& PubSubClient::setCallback(MQTT_CALLBACK_SIGNATURE) {
     this->callback = callback;
     return *this;
 }
diff --git a/src/PubSubClient.h b/src/PubSubClient.h
index 1098f66..f9792c0 100755
--- a/src/PubSubClient.h
+++ b/src/PubSubClient.h
@@ -73,7 +73,12 @@
 #define MQTTQOS1        (1 << 1)
 #define MQTTQOS2        (2 << 1)
 
-#define MQTT_CALLBACK_SIGNATURE void (*callback)(char*,uint8_t*,unsigned int)
+#ifdef ESP8266
+#include <functional>
+#define MQTT_CALLBACK_SIGNATURE std::function<void(char*, uint8_t*, uint32_t)> callback
+#else
+#define MQTT_CALLBACK_SIGNATURE void (*callback)(char*, uint8_t*, uint32_t)
+#endif
 
 class PubSubClient {
 private: