diff --git a/src/client.py b/src/client.py
--- a/src/client.py
+++ b/src/client.py
@@ -151,6 +151,7 @@ class Client(NetNode):
 		print(datetime.now(), "receiving data:")
 		progress = Progress(len(blocks_to_transfer))
 
+		last_flushed = datetime.now().timestamp()
 		for k in range(0, len(blocks_to_transfer), conf.batch_size.data):
 			indices = blocks_to_transfer[k:k+conf.batch_size.data]
 			self._outcoming.write_msg({"command": "req", "index": indices, "dataType": "data"})
@@ -160,10 +161,14 @@ class Client(NetNode):
 				block = bin_data[j*HashTree.BLOCK_SIZE:(j+1)*HashTree.BLOCK_SIZE]
 				data_file.write_at(i, block)
 
+				log.info("block #{0}: {1}...{2}".format(i, block[:5], block[-5:]))
 				if self._tree_file:
 					self._new_leaves[i+self._tree.leaf_start] = hash_block(block)
 
-				log.info("block #{0}: {1}...{2}".format(i, block[:5], block[-5:]))
+					t = datetime.now().timestamp()
+					if t-last_flushed >= 60 and self._tree_file:
+						self._update_tree()
+						last_flushed = t
 
 				stats.log_transferred_block()
 				progress.p(k+j)