diff --git a/taggit/managers.py b/taggit/managers.py
index 2464640a..a54bf1dc 100644
--- a/taggit/managers.py
+++ b/taggit/managers.py
@@ -204,7 +204,9 @@ def _to_tag_model_instances(self, tags, tag_kwargs):
         tag_objs = set()
 
         for t in tags:
-            if isinstance(t, self.through.tag_model()):
+            if hasattr(t, "first") and isinstance(t.first(), self.through.tag_model()):
+                tag_objs.add(t.first())
+            elif isinstance(t, self.through.tag_model()):
                 tag_objs.add(t)
             elif isinstance(t, str):
                 str_tags.add(t)