diff --git a/src/monitor_utils/runner.py b/src/monitor_utils/runner.py
index d8c3993..5f0aa5a 100644
--- a/src/monitor_utils/runner.py
+++ b/src/monitor_utils/runner.py
@@ -211,7 +211,7 @@ def build_product_details(
         if not bypass_thresholds and not passes_percentage and not passes_price_drop:
             return
 
-    built = Product(
+    built_product = Product(
         product_id=product_id,
         title=product["title"],
         url=product["url"],
@@ -227,6 +227,7 @@ def build_product_details(
             promo_dollar_off=product.get("promoDollarOff"),
             promo_min_spend=product.get("promoMinSpend"),
             new_listing=new_listing,
+            asin=product.get("asin"),
         ),
         timing=ProductTiming(
             discovered_date=product["discoveredDate"],
@@ -249,7 +250,7 @@ def build_product_details(
             member_deal=product["memberDeal"],
         ),
     )
-    return built
+    return built_product
 
 
 async def run_monitor_cycle(
diff --git a/tests/test_build_product_details.py b/tests/test_build_product_details.py
index 1ef0c25..0d61676 100644
--- a/tests/test_build_product_details.py
+++ b/tests/test_build_product_details.py
@@ -78,6 +78,17 @@ def test_promo_fields_read_through():
     assert product.metadata.percentage == 20
 
 
+def test_asin_reads_through():
+    """asin round-trips: convert_product_to_mongo writes it, so the consumer
+    must read it back for the SellerAmp lookup"""
+    product = build_product_details(_doc(asin="B0CHX3QBCH"), min_percentage=0)
+    assert product.metadata.asin == "B0CHX3QBCH"
+
+
+def test_missing_asin_defaults_to_none():
+    assert build_product_details(_doc(), min_percentage=0).metadata.asin is None
+
+
 def test_missing_promo_keys_default_to_none():
     """a doc from a lagging monitor lacks promo keys -> None, not KeyError"""
     product = build_product_details(_doc(), min_percentage=0)