diff --git a/scrapy/responsetypes.py b/scrapy/responsetypes.py
index 632787e06..fd7310c80 100644
--- a/scrapy/responsetypes.py
+++ b/scrapy/responsetypes.py
@@ -9,6 +9,7 @@ from urllib.parse import urlparse
 from warnings import warn
 
 from xtractmime import RESOURCE_HEADER_BUFFER_LENGTH, extract_mime
+from xtractmime._utils import contains_binary
 
 from scrapy.exceptions import ScrapyDeprecationWarning
 from scrapy.http import Response
@@ -127,7 +128,11 @@ class ResponseTypes:
             filename = url
 
         if filename:
-            return (self.mimetypes.guess_type(filename)[0].encode(),)
+            mimetype, encoding = self.mimetypes.guess_type(filename)
+            if encoding:
+                return (f"application/{encoding}".encode(),)
+            else:
+                return (mimetype.encode(),)
 
         return None
 
@@ -137,7 +142,16 @@ class ResponseTypes:
         if not body:
             body = b''
 
-        body = body[:RESOURCE_HEADER_BUFFER_LENGTH].replace(b"\x00", b"")
+        contains_binary_bytes = False
+
+        for index in range(len(body)):
+            if body[index:index + 1] != b"\x00" and contains_binary(body[index:index + 1]):
+                contains_binary_bytes = True
+                break
+
+        if not contains_binary_bytes:
+            body = body[:RESOURCE_HEADER_BUFFER_LENGTH].replace(b"\x00", b"")
+
         cls = Response
         http_origin = not url or urlparse(url).scheme in ("http", "https")
         content_types = self._guess_content_type(headers=headers, url=url, filename=filename)
diff --git a/tests/test_responsetypes.py b/tests/test_responsetypes.py
index 69ee1341e..9a07dc2f8 100644
--- a/tests/test_responsetypes.py
+++ b/tests/test_responsetypes.py
@@ -76,9 +76,9 @@ class ResponseTypesTest(unittest.TestCase):
         mappings = [
             ({'url': 'http://www.example.com/data.csv'}, TextResponse),
             ({'headers': Headers({'Content-Type': ['text/html; charset=utf-8']}),
-              'url': 'http://www.example.com/item/'}, HtmlResponse), # Failing with xtractmime, returning TextResponse expected HtmlResponse
+              'url': 'http://www.example.com/item/'}, HtmlResponse),
             ({'headers': Headers({'Content-Disposition': ['attachment; filename="data.xml.gz"']}),
-              'url': 'http://www.example.com/page/'}, Response), # Failing with xtractmime, returning TextResponse expected Response
+              'url': 'http://www.example.com/page/'}, Response),
         ]
         for source, cls in mappings:
             retcls = responsetypes.from_args(**source)
@@ -86,19 +86,19 @@ class ResponseTypesTest(unittest.TestCase):
 
     def test_from_args_post_xtractmime(self):
         mappings = [
-            ({'body': b'Some plain text data with tabs and null bytes'}, TextResponse),
-            ({'body': b'\x03\x02\xdf\xdd\x23', 'headers': Headers({'Content-Encoding': 'UTF-8'})}, 
+            ({'body': b'Some plain\0 text data with\0 tabs and null bytes\0'}, TextResponse),
+            ({'body': b'\x03\x02\xdf\xdd\x23', 'headers': Headers({'Content-Encoding': 'UTF-8'})},
              Response),
             # different behaviour with http and non-http urls
-            ({'body': b'\x00\xfe\xff', 'url': 'http://www.example.com/item/',
-              'headers': Headers({'Content-Type': b'text/plain'})}, Response), 
-            ({'body': b'\x00\xfe\xff', 'url': '://www.example.com/item/',
+            ({'body': b'\x00\x01\xff', 'url': 'http://www.example.com/item/',
+              'headers': Headers({'Content-Type': b'text/plain'})}, Response),
+            ({'body': b'\x00\x01\xff', 'url': '://www.example.com/item/',
               'headers': Headers({'Content-Type': b'text/plain'})}, TextResponse),
-            ({'url': 'http://www.example.com/item/file.html'}, HtmlResponse), # Failing with xtractmime, return TextResponse expected HtmlResponse
-            ({'body': b'Some plain text\ndata with tabs\t and null bytes\0'}, Response), # earlier expected to be binary response, refer "test_from_body()"
+            ({'url': 'http://www.example.com/item/file.html'}, HtmlResponse),
+            ({'body': b'Some plain text data\1 with tabs and\n null bytes\0'}, Response),
             ({'body': b'<html><head><title>Hello</title></head>'}, HtmlResponse),
             ({'body': b'<?xml version="1.0" encoding="utf-8"'}, XmlResponse),
-            ({'filename': 'file.html'}, HtmlResponse), # Failing with xtractmime, returning TextResponse expected HtmlResponse
+            ({'filename': 'file.html'}, HtmlResponse),
         ]
         for source, cls in mappings:
             retcls = responsetypes.from_args(**source)