diff --git a/mongoose.h b/mongoose.h
index 958b5c72..f25d7ad5 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -2690,6 +2690,25 @@ bool mg_ota_end(void);                           // Stop writing
 
 
 
+#if MG_OTA != MG_OTA_NONE && MG_OTA != MG_OTA_CUSTOM
+
+struct mg_flash {
+  void *start;    // Address at which flash starts
+  size_t size;    // Flash size
+  size_t secsz;   // Sector size
+  size_t align;   // Write alignment
+  bool (*write_fn)(void *, const void *, size_t);  // Write function
+  bool (*swap_fn)(void);                           // Swap partitions
+};
+
+bool mg_ota_flash_begin(size_t new_firmware_size, struct mg_flash *flash);
+bool mg_ota_flash_write(const void *buf, size_t len, struct mg_flash *flash);
+bool mg_ota_flash_end(struct mg_flash *flash);
+
+#endif
+
+
+