diff --git a/bitbake/lib/bb/data_smart.py b/bitbake/lib/bb/data_smart.py
index 833d9f17a4..742c7fb64a 100644
--- a/bitbake/lib/bb/data_smart.py
+++ b/bitbake/lib/bb/data_smart.py
@@ -123,7 +123,7 @@ class VariableParse:
 
             for k in parser.contains:
                 if k not in self.contains:
-                    self.contains[k] = parser.contains[k]
+                    self.contains[k] = parser.contains[k].copy()
                 else:
                     self.contains[k].update(parser.contains[k])
             value = utils.better_eval(codeobj, DataContext(self.d))