diff --git a/tests/py3-ignores.txt b/tests/py3-ignores.txt
index 9d84e7634..0265f2985 100644
--- a/tests/py3-ignores.txt
+++ b/tests/py3-ignores.txt
@@ -25,7 +25,6 @@ tests/test_downloadermiddleware_retry.py
 tests/test_downloadermiddleware_robotstxt.py
 tests/test_downloadermiddleware_stats.py
 tests/test_downloadermiddleware_useragent.py
-tests/test_dupefilters.py
 tests/test_engine.py
 tests/test_http_cookies.py
 tests/test_logformatter.py
diff --git a/tests/test_dupefilters.py b/tests/test_dupefilters.py
index f8f800a72..8de50f004 100644
--- a/tests/test_dupefilters.py
+++ b/tests/test_dupefilters.py
@@ -3,6 +3,7 @@ import unittest
 
 from scrapy.dupefilters import RFPDupeFilter
 from scrapy.http import Request
+from scrapy.utils.python import to_bytes
 
 
 class RFPDupeFilterTest(unittest.TestCase):
@@ -43,7 +44,7 @@ class RFPDupeFilterTest(unittest.TestCase):
 
             def request_fingerprint(self, request):
                 fp = hashlib.sha1()
-                fp.update(request.url.lower())
+                fp.update(to_bytes(request.url.lower()))
                 return fp.hexdigest()
 
         case_insensitive_dupefilter = CaseInsensitiveRFPDupeFilter()