diff --git a/Scripts/deduplicate.py b/Scripts/deduplicate.py
index 4f1a5a1..3dddf34 100755
--- a/Scripts/deduplicate.py
+++ b/Scripts/deduplicate.py
@@ -19,6 +19,8 @@
 
 from common import is_valid_domain, write_lines
 
+HEADER_PREFIXES = ("! ", "#", "[", ";")
+
 
 @dataclass(slots=True)
 class Stats:
@@ -34,7 +36,7 @@ def compression_ratio(self) -> float:
 
 def is_header(line: str) -> bool:
     """Check if line is a header/metadata line"""
-    return line.startswith(("! ", "#", "[", ";")) or not line
+    return line.startswith(HEADER_PREFIXES) or not line
 
 
 def is_valid_rule(line: str) -> bool:
diff --git a/Scripts/update-lists.py b/Scripts/update-lists.py
index 6bc4d15..29660fe 100644
--- a/Scripts/update-lists.py
+++ b/Scripts/update-lists.py
@@ -32,6 +32,7 @@
 SOURCES_CONFIG: Final[str] = "lists/sources-urls.json"
 DEFAULT_OUTPUT: Final[str] = "lists/sources"
 METADATA_FILE: Final[str] = "lists/sources-metadata.json"
+HEADER_PREFIXES: Final[tuple[str, ...]] = ("! ", "#", "[")
 TIMEOUT: Final[int] = 60
 CHUNK_SIZE: Final[int] = 65536
 MAX_CONCURRENT: Final[int] = 10
@@ -90,7 +91,7 @@ def count_rules(content: str) -> int:
     return sum(
         1
         for line in io.StringIO(content)
-        if (stripped := line.strip()) and not stripped.startswith(("! ", "#", "["))
+        if (stripped := line.strip()) and not stripped.startswith(HEADER_PREFIXES)
     )