diff --git a/tools/kwbimage.c b/tools/kwbimage.c
index 4e9ba5ddfae..b6deb978f61 100644
--- a/tools/kwbimage.c
+++ b/tools/kwbimage.c
@@ -2184,8 +2184,14 @@ static int kwbimage_generate_config(void *ptr, struct image_tool_params *params)
 	if (mhdr->blockid == IBR_HDR_NAND_ID)
 		fprintf(f, "NAND_PAGE_SIZE 0x%x\n", (unsigned)le16_to_cpu(mhdr->nandpagesize));
 
-	if (version != 0 && mhdr->blockid == IBR_HDR_NAND_ID)
-		fprintf(f, "NAND_BLKSZ 0x%x\n", (unsigned)mhdr->nandblocksize);
+	if (version != 0 && mhdr->blockid == IBR_HDR_NAND_ID) {
+		if (mhdr->nandblocksize != 0) /* block size explicitly set in 64 kB unit */
+			fprintf(f, "NAND_BLKSZ 0x%x\n", (unsigned)mhdr->nandblocksize * 64*1024);
+		else if (le16_to_cpu(mhdr->nandpagesize) > 512)
+			fprintf(f, "NAND_BLKSZ 0x10000\n"); /* large page NAND flash = 64 kB block size */
+		else
+			fprintf(f, "NAND_BLKSZ 0x4000\n"); /* small page NAND flash = 16 kB block size */
+	}
 
 	if (mhdr->blockid == IBR_HDR_NAND_ID && (version != 0 || is_v0_ext))
 		fprintf(f, "NAND_BADBLK_LOCATION 0x%x\n", (unsigned)mhdr->nandbadblklocation);