diff --git a/core/dbt/adapters/base/impl.py b/core/dbt/adapters/base/impl.py
index 014f89902ef..03d8f4a2f8c 100644
--- a/core/dbt/adapters/base/impl.py
+++ b/core/dbt/adapters/base/impl.py
@@ -734,7 +734,7 @@ def list_relations(self, database: Optional[str], schema: str) -> List[BaseRelat
                 # for relation in cache_schemas:
                 #     cache_update.add((database, schema))
 
-                self.cache.update_schemas(set((database, schema)))
+                self.cache.update_schemas([(database, schema)])
 
         fire_event(
             ListRelations(