diff --git a/stride/problem/acquisitions.py b/stride/problem/acquisitions.py
index 10363ae..a48513e 100644
--- a/stride/problem/acquisitions.py
+++ b/stride/problem/acquisitions.py
@@ -482,9 +482,11 @@ def __set_desc__(self, description, **kwargs):
 
         self.id = description.id
 
+        self._source_ids = []
         for source_id in description.source_ids:
             self._source_ids.append(source_id)
 
+        self._receiver_ids = []
         for receiver_id in description.receiver_ids:
             self._receiver_ids.append(receiver_id)