diff --git a/lib/RecordModel/AutoFileReader.rb b/lib/RecordModel/AutoFileReader.rb
index 9252bce..0ec0e35 100644
--- a/lib/RecordModel/AutoFileReader.rb
+++ b/lib/RecordModel/AutoFileReader.rb
@@ -3,6 +3,7 @@
 class AutoFileReader
   def self.open(path, buflen=2**16, &block)
     obj = _open(path, buflen)
+    raise unless obj
     if block
       begin
         block.call(obj)