diff --git a/include/part.h b/include/part.h
index f89ebc6e731a5029c98b40fbb3ab00df98c9d2d0..4f5a570795b8c5d4cc1901641c177bea4f2301d0 100644
--- a/include/part.h
+++ b/include/part.h
@@ -45,6 +45,10 @@ typedef struct block_dev_desc {
 				      unsigned long start,
 				      lbaint_t blkcnt,
 				      unsigned long *buffer);
+	unsigned long	(*block_write)(int dev,
+				       unsigned long start,
+				       lbaint_t blkcnt,
+				       const void *buffer);
 }block_dev_desc_t;
 
 /* Interface types: */