diff --git a/scrapy/downloadermiddlewares/httpcompression.py b/scrapy/downloadermiddlewares/httpcompression.py
index 95bc1849d..6c8b659bd 100644
--- a/scrapy/downloadermiddlewares/httpcompression.py
+++ b/scrapy/downloadermiddlewares/httpcompression.py
@@ -93,7 +93,7 @@ class HttpCompressionMiddleware:
                         f"({len(response.body)} B) exceeded DOWNLOAD_MAXSIZE "
                         f"({self._max_size} B) during decompression."
                     )
-                if len(response.body) < warn_size and len(decoded_body) >= warn_size:
+                if len(response.body) < warn_size <= len(decoded_body):
                     logger.warning(
                         f"{response} body size after decompression "
                         f"({len(decoded_body)} B) is larger than the "
diff --git a/scrapy/spiders/sitemap.py b/scrapy/spiders/sitemap.py
index 0574f0ccb..386aa6a6e 100644
--- a/scrapy/spiders/sitemap.py
+++ b/scrapy/spiders/sitemap.py
@@ -22,6 +22,8 @@ class SitemapSpider(Spider):
     sitemap_rules = [("", "parse")]
     sitemap_follow = [""]
     sitemap_alternate_links = False
+    _max_size: int
+    _warn_size: int
 
     @classmethod
     def from_crawler(cls, crawler: "Crawler", *args: Any, **kwargs: Any) -> "Self":
@@ -97,7 +99,7 @@ class SitemapSpider(Spider):
                 body = gunzip(response.body, max_size=max_size)
             except _DecompressionMaxSizeExceeded:
                 return None
-            if uncompressed_size < warn_size and len(body) >= warn_size:
+            if uncompressed_size < warn_size <= len(body):
                 logger.warning(
                     f"{response} body size after decompression ({len(body)} B) "
                     f"is larger than the download warning size ({warn_size} B)."