diff --git a/httpd/httpd.c b/httpd/httpd.c
index 9e33f1a..30b1118 100644
--- a/httpd/httpd.c
+++ b/httpd/httpd.c
@@ -14,9 +14,6 @@
 #define SESSION_ID_LENGTH 12
 #define SESSION_TIMEOUT 200
 
-// SPI FLASH MEMORY PAGE SIZE.
-#define FLASHMEM_PAGE_SIZE 0x100
-
 #define CMARK_S 6
 
 #pragma codeseg BANK1
@@ -330,18 +327,22 @@ uint8_t stream_upload(uint16_t bptr)
 			}
 			crc16(p + bptr);
 			flash_buf[write_len++] = p[bptr++];
-			if (write_len >= FLASHMEM_PAGE_SIZE) {
+			if (write_len >= FLASH_PAGE_SIZE) {
 				dbg_string("len: "); dbg_short(write_len); dbg_char(' ');
 				dbg_string("CRC16: "); dbg_short(crc_value); dbg_char('\n');
+				if (uptr % FLASH_SECTOR_SIZE == 0) {
+					flash_region.addr = uptr;
+					flash_sector_erase();
+				}
 				flash_region.addr = uptr;
-				flash_region.len = FLASHMEM_PAGE_SIZE;
+				flash_region.len = FLASH_PAGE_SIZE;
 				flash_write_bytes(flash_buf);
-				uptr += FLASHMEM_PAGE_SIZE;
-				write_len -= FLASHMEM_PAGE_SIZE;
+				uptr += FLASH_PAGE_SIZE;
+				write_len -= FLASH_PAGE_SIZE;
 
 				// Copy the remaining byte for the next page to the beginning of the buffer.
 				if (write_len > 0) {
-					memcpy(flash_buf, flash_buf + FLASHMEM_PAGE_SIZE, write_len);
+					memcpy(flash_buf, flash_buf + FLASH_PAGE_SIZE, write_len);
 				}
 			}
 			bindex = 0;
diff --git a/rtl837x_flash.h b/rtl837x_flash.h
index 60de64f..5280258 100644
--- a/rtl837x_flash.h
+++ b/rtl837x_flash.h
@@ -1,6 +1,16 @@
 #ifndef _RTL837X_FLASH_H_
 #define _RTL837X_FLASH_H_
 
+// SPI FLASH MEMORY PAGE SIZE.
+#define FLASH_PAGE_SIZE 0x100
+// SPI FLASH MEMORY SECTOR SIZE = ERASE SIZE.
+#define FLASH_SECTOR_SIZE 0x1000
+
+#if (FLASH_SECTOR_SIZE % FLASH_PAGE_SIZE) != 0
+#error "FLASH_SECTOR_SIZE must be a multiple of FLASH_PAGE_SIZE"
+#endif
+
+
 void flash_init(uint8_t enable_dio);
 void flash_read_uid(void);
 void flash_write_enable(void);