Merge "Detect back_populates referring to non-relationship"

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/sqlalchemy/orm/relationships.py b/lib/sqlalchemy/orm/relationships.py
index 5d87ef797..00a14b04c 100644
--- a/lib/sqlalchemy/orm/relationships.py
+++ b/lib/sqlalchemy/orm/relationships.py
@@ -2046,6 +2046,13 @@ class RelationshipProperty(StrategizedProperty):
 
     def _add_reverse_property(self, key):
         other = self.mapper.get_property(key, _configure_mappers=False)
+        if not isinstance(other, RelationshipProperty):
+            raise sa_exc.InvalidRequestError(
+                "back_populates on relationship '%s' refers to attribute '%s' "
+                "that is not a relationship.  The back_populates parameter "
+                "should refer to the name of a relationship on the target "
+                "class." % (self, other)
+            )
         # viewonly and sync_backref cases
         # 1. self.viewonly==True and other.sync_backref==True -> error
         # 2. self.viewonly==True and other.viewonly==False and