diff --git a/examples/device/dfu_freertos/src/main.c b/examples/device/dfu_freertos/src/main.c
index 69d0bb0ec..206f30dd4 100644
--- a/examples/device/dfu_freertos/src/main.c
+++ b/examples/device/dfu_freertos/src/main.c
@@ -40,6 +40,8 @@
   #include "freertos/task.h"
   #include "freertos/timers.h"
   #include "esp_log.h"
+  #include "esp_partition.h"
+  #include "esp_ota_ops.h"
 
   #define USBD_STACK_SIZE     4096
 #else
@@ -238,6 +240,16 @@ uint16_t tud_dfu_upload_cb(uint8_t alt, uint16_t block_num, uint8_t* data, uint1
     return 0;
   }
 
+  ESP_LOGD(TAG, "upload, alt=%u block=%u", alt, block_num);
+  const esp_partition_t * part  = esp_partition_find_first(ESP_PARTITION_TYPE_APP, ESP_PARTITION_SUBTYPE_APP_OTA_0, NULL);
+  esp_err_t rc = esp_partition_read(part, block_num * CFG_TUD_DFU_XFER_BUFSIZE, data, length);
+  if (ESP_OK == rc) {
+    xfer_len = length;
+  } else {
+    xfer_len = 0;
+    ESP_LOGW(TAG, "reading flash failed");
+  }
+
   return xfer_len;
 }