diff --git a/tldp/sources.py b/tldp/sources.py
index 14f87ea..2d76bf4 100644
--- a/tldp/sources.py
+++ b/tldp/sources.py
@@ -184,7 +184,7 @@ class SourceDocument(object):
         self.doctype = guess(self.filename)
         self.status = 'source'
         self.output = None
-        self.build = None
+        self.working = None
         self.newer = set()
         self.dirname, self.basename = os.path.split(self.filename)
         self.stem, self.ext = stem_and_ext(self.basename)