--- a/bitbake/lib/bb/data_smart.py
+++ b/bitbake/lib/bb/data_smart.py
@@ -174,7 +174,14 @@ class IncludeHistory(object):
         self.filename = filename or '[TOP LEVEL]'
         self.children = []
         self.current = self
-        self.variables = {}
+        self.variables = COWDictBase.copy()
+
+    def copy(self):
+        new = IncludeHistory(self.parent, self.filename, self.datasmart)
+        new.children = copy.deepcopy(self.children)
+        new.current = self.current
+        new.variables = self.variables.copy()
+        return new
 
     def include(self, filename):
         newfile = IncludeHistory(self.current, filename)
@@ -615,7 +622,7 @@ class DataSmart(MutableMapping):
         # we really want this to be a DataSmart...
         data = DataSmart(seen=self._seen_overrides.copy(), special=self._special_values.copy())
         data.dict["_data"] = self.dict
-        data.history = copy.deepcopy(self.history)
+        data.history = self.history.copy()
         data.history.datasmart = data
         data._tracking = self._tracking