diff --git a/src/block.js b/src/block.js
index dca1f4c..5d4dc1a 100644
--- a/src/block.js
+++ b/src/block.js
@@ -44,11 +44,10 @@ Block.fromBuffer = function (buffer) {
     return vi.number
   }
 
-  // FIXME: poor performance
   function readTransaction () {
     var tx = Transaction.fromBuffer(buffer.slice(offset), true)
 
-    offset += tx.toBuffer().length
+    offset += tx.byteLength()
     return tx
   }