diff --git a/src/strawberry_sqlalchemy_mapper/loader.py b/src/strawberry_sqlalchemy_mapper/loader.py
index f2ed0d5..64d684c 100644
--- a/src/strawberry_sqlalchemy_mapper/loader.py
+++ b/src/strawberry_sqlalchemy_mapper/loader.py
@@ -77,11 +77,11 @@ async def load_fn(keys: List[Tuple]) -> List[Any]:
                     # Use another query when relationship uses a secondary table
                     self_model = relationship.parent.entity
 
-                    self_model_key_label = relationship.local_remote_pairs[0][1].key
-                    related_model_key_label = relationship.local_remote_pairs[1][1].key
+                    self_model_key_label = str(relationship.local_remote_pairs[0][1].key)
+                    related_model_key_label = str(relationship.local_remote_pairs[1][1].key)
 
-                    self_model_key = relationship.local_remote_pairs[0][0].key
-                    related_model_key = relationship.local_remote_pairs[1][0].key
+                    self_model_key = str(relationship.local_remote_pairs[0][0].key)
+                    related_model_key = str(relationship.local_remote_pairs[1][0].key)
 
                     remote_to_use = relationship.local_remote_pairs[0][1]
                     query_keys = tuple([item[0] for item in keys])
diff --git a/src/strawberry_sqlalchemy_mapper/mapper.py b/src/strawberry_sqlalchemy_mapper/mapper.py
index 542cff4..d734396 100644
--- a/src/strawberry_sqlalchemy_mapper/mapper.py
+++ b/src/strawberry_sqlalchemy_mapper/mapper.py
@@ -517,14 +517,18 @@ async def resolve(self, info: Info):
                     )
                 else:
                     # If has a secondary table, gets only the first ID as additional IDs require a separate query
-                    local_remote_pairs_secondary_table_local = relationship.local_remote_pairs[
-                        0][0]
-                    relationship_key = tuple(
-                        [
-                            getattr(
-                                self, str(local_remote_pairs_secondary_table_local.key)),
-                        ]
-                    )
+                    relationship_key = ()
+                    if relationship.local_remote_pairs:
+                        local_remote_pairs_secondary_table_local = relationship.local_remote_pairs[0][0]
+                        relationship_key = tuple(
+                            [
+                                getattr(
+                                    self, str(local_remote_pairs_secondary_table_local.key)),
+                            ]
+                        )
+                    return relationship_key
+
+
 
                 if any(item is None for item in relationship_key):
                     if relationship.uselist: