[1.7.x] Fixed #23090: Document and enforce not double-squashing migrations

1 files changed, 2 insertions, 0 deletions

diff --git a/django/core/management/commands/squashmigrations.py b/django/core/management/commands/squashmigrations.py
index c4f9326c5d..8795947296 100644
--- a/django/core/management/commands/squashmigrations.py
+++ b/django/core/management/commands/squashmigrations.py
@@ -70,6 +70,8 @@ class Command(BaseCommand):
         # Load the operations from all those migrations and concat together
         operations = []
         for smigration in migrations_to_squash:
+            if smigration.replaces:
+                raise CommandError("You cannot squash squashed migrations! Please transition it to a normal migration first: https://docs.djangoproject.com/en/1.7/topics/migrations/#squashing-migrations")
             operations.extend(smigration.operations)
 
         if self.verbosity > 0: