diff --git a/include/spartan3.h b/include/spartan3.h
index 30b1c2d..d5a589d 100644
--- a/include/spartan3.h
+++ b/include/spartan3.h
@@ -57,6 +57,7 @@
 	Xilinx_done_fn	done;
 	Xilinx_wr_fn	wr;
 	Xilinx_post_fn	post;
+	Xilinx_bwr_fn	bwr; /* block write function */
 } Xilinx_Spartan3_Slave_Serial_fns;
 
 /* Device Image Sizes
diff --git a/include/xilinx.h b/include/xilinx.h
index d0799bc..2cb2e5b 100644
--- a/include/xilinx.h
+++ b/include/xilinx.h
@@ -100,5 +100,6 @@
 typedef int (*Xilinx_abort_fn)( int cookie );
 typedef int (*Xilinx_pre_fn)( int cookie );
 typedef int (*Xilinx_post_fn)( int cookie );
+typedef int (*Xilinx_bwr_fn)( void *buf, size_t len, int flush, int cookie );
 
 #endif  /* _XILINX_H_ */