diff --git a/src/client.py b/src/client.py
--- a/src/client.py
+++ b/src/client.py
@@ -166,8 +166,10 @@ class Client(NetNode):
 					self._new_leaves[i+self._tree.leaf_start] = hash_block(block)
 
 					t = datetime.now().timestamp()
-					if t-last_flushed >= 60 and self._tree_file:
-						self._update_tree()
+					if t-last_flushed >= 60:
+						if self._tree_file:
+							self._update_tree()
+						self._refresh_lock()
 						last_flushed = t
 
 				stats.log_transferred_block()