Fixed #31863 -- Prevented mutating model state by copies of model instances.

Regression in bfb746f983aa741afa3709794e70f1e0ab6040b5.

1 files changed, 4 insertions, 1 deletions

diff --git a/django/db/models/base.py b/django/db/models/base.py
index 3792ffb90e..7c7bd2d7ee 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -546,7 +546,10 @@ class Model(metaclass=ModelBase):
 
     def __getstate__(self):
         """Hook to allow choosing the attributes to pickle."""
-        return self.__dict__
+        state = self.__dict__.copy()
+        state['_state'] = copy.copy(state['_state'])
+        state['_state'].fields_cache = state['_state'].fields_cache.copy()
+        return state
 
     def __setstate__(self, state):
         pickled_version = state.get(DJANGO_VERSION_PICKLE_KEY)