diff --git a/bigfile/__init__.py b/bigfile/__init__.py
index <HASH>..<HASH> 100644
--- a/bigfile/__init__.py
+++ b/bigfile/__init__.py
@@ -56,6 +56,7 @@ class BigFile(BigFileBase):
 
     def __init__(self, filename, create=False):
         BigFileBase.__init__(self, filename, create)
+        del self._blocks
 
     @property
     def blocks(self):
serial API will rewalk .blocks upon first request.