diff --git a/src/Arduino_ESP32_OTA.cpp b/src/Arduino_ESP32_OTA.cpp
index 76c1d02..dbc0fae 100644
--- a/src/Arduino_ESP32_OTA.cpp
+++ b/src/Arduino_ESP32_OTA.cpp
@@ -91,7 +91,6 @@ void Arduino_ESP32_OTA::setMagic(uint32_t magic)
 void Arduino_ESP32_OTA::write_byte_to_flash(uint8_t data)
 {
   Update.write(&data, 1);
-  _context->writtenBytes++;
 }
 
 int Arduino_ESP32_OTA::startDownload(const char * ota_url)
@@ -103,7 +102,10 @@ int Arduino_ESP32_OTA::startDownload(const char * ota_url)
   int statusCode;
   int res;
 
-  _context = new Context(ota_url, std::bind(&Arduino_ESP32_OTA::write_byte_to_flash, this, std::placeholders::_1));
+  _context = new Context(ota_url, [this](uint8_t data){
+    _context->writtenBytes++;
+    write_byte_to_flash(data);
+  });
 
   if(strcmp(_context->parsed_url.schema(), "http") == 0) {
     _client = new WiFiClient();