diff --git a/tradein-mvp/backend/app/services/scrapers/avito_imv.py b/tradein-mvp/backend/app/services/scrapers/avito_imv.py
index bd9b8aa6..3113b89d 100644
--- a/tradein-mvp/backend/app/services/scrapers/avito_imv.py
+++ b/tradein-mvp/backend/app/services/scrapers/avito_imv.py
@@ -334,6 +334,8 @@ def _raise_for_status_categorized(resp: Any, context: str) -> None:
     if status >= 500:
         raise IMVTransientError(f"Avito {context}: HTTP {status} — transient server error")
     if status >= 400:
+        body_preview = (resp.text or "")[:200]
+        logger.warning("Avito %s HTTP %d: body=%r", context, status, body_preview)
         resp.raise_for_status()  # other 4xx → standard HTTPStatusError
 
 
diff --git a/tradein-mvp/scripts/backfill-house-imv.py b/tradein-mvp/scripts/backfill-house-imv.py
index 3b58658f..48b8a38b 100644
--- a/tradein-mvp/scripts/backfill-house-imv.py
+++ b/tradein-mvp/scripts/backfill-house-imv.py
@@ -51,6 +51,25 @@ logging.basicConfig(
 )
 logger = logging.getLogger("phase-c")
 
+# Avito IMV API accepts only these house_type values (verified 2026-05-24).
+# Our `listings.house_type` may contain pre-2026 values like 'monolith' / 'monolith_brick'.
+_HOUSE_TYPE_TO_IMV = {
+    "panel": "panel",
+    "brick": "brick",
+    "monolith": "monolithic",       # API renamed; raw value rejected with 400
+    "monolithic": "monolithic",
+    "monolith_brick": "monolithic",  # API doesn't accept hybrid → fall back to monolithic
+    "block": "block",
+    "wood": "wood",
+}
+_HOUSE_TYPE_DEFAULT = "panel"  # most common in EKB; safe default for unknown
+
+
+def _map_house_type(raw: str | None) -> str:
+    if not raw:
+        return _HOUSE_TYPE_DEFAULT
+    return _HOUSE_TYPE_TO_IMV.get(raw.lower().strip(), _HOUSE_TYPE_DEFAULT)
+
 DATABASE_URL = os.environ.get("DATABASE_URL")
 if not DATABASE_URL:
     raise SystemExit(
@@ -92,12 +111,8 @@ def pick_lot_params(db: Session, house_id: int) -> dict:
         "rooms": int(row["rooms"]),
         "area_m2": float(row["area_m2"]),
         "floor": int(row["floor"] or 1),
-        "floor_at_home": int(
-            row["total_floors"] or (house and house["total_floors"]) or 9
-        ),
-        "house_type": (
-            row["house_type"] or (house and house["house_type"]) or "panel"
-        ),
+        "floor_at_home": int(row["total_floors"] or (house and house["total_floors"]) or 9),
+        "house_type": _map_house_type(row["house_type"] or (house and house["house_type"])),
         "renovation_type": "cosmetic",
         "has_balcony": True,
         "has_loggia": False,