diff --git a/ndcube/ndcube.py b/ndcube/ndcube.py
index e285ecfa6..3671c80cd 100644
--- a/ndcube/ndcube.py
+++ b/ndcube/ndcube.py
@@ -966,6 +966,7 @@ def __neg__(self):
         return self._new_instance(data=-self.data)
 
     def add(self, value):
+        # Version at 22/Jan.
         kwargs = {}
         if isinstance(value, NDData) and value.wcs is None:
             if self.unit is not None and value.unit is not None: