Fixed #26819 -- Fixed BaseModelFormSet.validate_unique() "unhashable type: list" crash.

1 files changed, 6 insertions, 2 deletions

diff --git a/django/forms/models.py b/django/forms/models.py
index 7f5e2544dd..aa35ef5f92 100644
--- a/django/forms/models.py
+++ b/django/forms/models.py
@@ -696,8 +696,12 @@ class BaseModelFormSet(BaseFormSet):
                     for field in unique_check if field in form.cleaned_data
                 )
                 # Reduce Model instances to their primary key values
-                row_data = tuple(d._get_pk_val() if hasattr(d, '_get_pk_val') else d
-                                 for d in row_data)
+                row_data = tuple(
+                    d._get_pk_val() if hasattr(d, '_get_pk_val')
+                    # Prevent "unhashable type: list" errors later on.
+                    else tuple(d) if isinstance(d, list)
+                    else d for d in row_data
+                )
                 if row_data and None not in row_data:
                     # if we've already seen it then we have a uniqueness failure
                     if row_data in seen_data: