diff --git a/emmet-api/app.py b/emmet-api/app.py
index 2f05c727f0..4b6fbc89d8 100644
--- a/emmet-api/app.py
+++ b/emmet-api/app.py
@@ -198,7 +198,7 @@
     alloy_pairs_store = MongoURIStore(
         uri=db_uri,
         database=f"mp_core_{db_suffix}",
-        key="material_id",
+        key="pair_id",
         collection_name="alloy_pairs",
     )