everythings passing, again.

2 files changed, 5 insertions, 7 deletions

diff --git a/alembic/migration.py b/alembic/migration.py
index d8077b7..4f5f342 100644
--- a/alembic/migration.py
+++ b/alembic/migration.py
@@ -692,7 +692,6 @@ class StampStep(MigrationStep):
     def __init__(self, from_, to_, is_upgrade, branch_move):
         self.from_ = util.to_tuple(from_, default=())
         self.to_ = util.to_tuple(to_, default=())
-        assert len(self.to_) <= 1
         self.is_upgrade = is_upgrade
         self.branch_move = branch_move
         self.migration_fn = self.stamp_revision
@@ -743,4 +742,4 @@ class StampStep(MigrationStep):
         return len(self.from_) > 1
 
     def should_unmerge_branches(self, heads):
-        return False
+        return len(self.to_) > 1
diff --git a/tests/test_version_table.py b/tests/test_version_table.py
index 5e333aa..2271180 100644
--- a/tests/test_version_table.py
+++ b/tests/test_version_table.py
@@ -7,21 +7,20 @@ from sqlalchemy.engine.reflection import Inspector
 from alembic import migration
 
 from alembic.util import CommandError
-from alembic import util
 
 version_table = Table('version_table', MetaData(),
                       Column('version_num', String(32), nullable=False))
 
 
 def _up(from_, to_, branch_presence_changed=False):
-    return migration.MigrationStep(
-        None, util.to_tuple(from_), to_, "", True, branch_presence_changed
+    return migration.StampStep(
+        from_, to_, True, branch_presence_changed
     )
 
 
 def _down(from_, to_, branch_presence_changed=False):
-    return migration.MigrationStep(
-        None, from_, util.to_tuple(to_), "", False, branch_presence_changed
+    return migration.StampStep(
+        from_, to_, False, branch_presence_changed
     )