diff --git a/scrapy/utils/gz.py b/scrapy/utils/gz.py
index 22cf58986..16c9ce539 100644
--- a/scrapy/utils/gz.py
+++ b/scrapy/utils/gz.py
@@ -62,4 +62,4 @@ def is_gzipped(response):
 
 
 def gzip_magic_number(response):
-    return response.body[:2] == b'\x1f\x8b'
+    return response.body[:3] == b'\x1f\x8b\x08'