diff --git a/flask_restx/fields.py b/flask_restx/fields.py
index 97957f7f..2526fa9d 100644
--- a/flask_restx/fields.py
+++ b/flask_restx/fields.py
@@ -323,6 +323,9 @@ def format(self, value):
         if isinstance(value, set):
             value = list(value)
 
+        if not isinstance(value, list) and hasattr(value, "__iter__"):
+            value = [i for i in value]
+ 
         is_nested = isinstance(self.container, Nested) or type(self.container) is Raw
 
         def is_attr(val):