diff --git a/scrapy/http/cookies.py b/scrapy/http/cookies.py
index a5329ad51..15f25f69d 100644
--- a/scrapy/http/cookies.py
+++ b/scrapy/http/cookies.py
@@ -166,7 +166,8 @@ class WrappedRequest:
         return name in self.request.headers
 
     def get_header(self, name, default=None):
-        return to_unicode(self.request.headers.get(name, default), errors="replace")
+        value = self.request.headers.get(name, default)
+        return to_unicode(value, errors="replace") if value is not None else None
 
     def header_items(self):
         return [
diff --git a/tests/test_http_cookies.py b/tests/test_http_cookies.py
index 9e43b72b0..db1c816d4 100644
--- a/tests/test_http_cookies.py
+++ b/tests/test_http_cookies.py
@@ -43,6 +43,13 @@ class WrappedRequestTest(TestCase):
     def test_get_header(self):
         self.assertEqual(self.wrapped.get_header("content-type"), "text/html")
         self.assertEqual(self.wrapped.get_header("xxxxx", "def"), "def")
+        self.assertEqual(self.wrapped.get_header("xxxxx"), None)
+        wrapped = WrappedRequest(
+            Request(
+                "http://www.example.com/page.html", headers={"empty-binary-header": b""}
+            )
+        )
+        self.assertEqual(wrapped.get_header("empty-binary-header"), "")
 
     def test_header_items(self):
         self.assertEqual(self.wrapped.header_items(), [("Content-Type", ["text/html"])])