diff --git a/scanner/config.py b/scanner/config.py
index c9b56eb..0042cc3 100644
--- a/scanner/config.py
+++ b/scanner/config.py
@@ -106,5 +106,7 @@ def _deep_update(base: dict, override: dict) -> None:
     for k, v in override.items():
         if isinstance(v, dict) and isinstance(base.get(k), dict):
             _deep_update(base[k], v)
+        elif v is None and isinstance(base.get(k), list):
+            pass  # YAML null on a list field = "not set" → keep default
         else:
             base[k] = v
diff --git a/scanner/differ.py b/scanner/differ.py
index 7b6d100..13be939 100644
--- a/scanner/differ.py
+++ b/scanner/differ.py
@@ -17,7 +17,7 @@ def normalize_text(text: str, cfg: dict) -> str:
     norm_cfg = cfg.get("normalization", {})
     if norm_cfg.get("collapse_whitespace", True):
         text = re.sub(r"\s+", " ", text).strip()
-    for pattern in norm_cfg.get("ignore_patterns", []):
+    for pattern in (norm_cfg.get("ignore_patterns") or []):
         text = re.sub(pattern, "[IGNORED]", text)
     return text
 
diff --git a/scanner/extractor.py b/scanner/extractor.py
index cde2d58..68aa669 100644
--- a/scanner/extractor.py
+++ b/scanner/extractor.py
@@ -47,7 +47,7 @@ def extract_page(html: str, url: str, cfg: dict | None = None) -> dict:
     soup = BeautifulSoup(html, "lxml")
 
     # Remove ignored selectors before text extraction
-    ignore_selectors = cfg.get("normalization", {}).get("ignore_selectors", [])
+    ignore_selectors = cfg.get("normalization", {}).get("ignore_selectors") or []
     for sel in ignore_selectors:
         for el in soup.select(sel):
             el.decompose()