diff --git a/scrapy/link.py b/scrapy/link.py
index dc6e64adc..2c8301680 100644
--- a/scrapy/link.py
+++ b/scrapy/link.py
@@ -4,7 +4,10 @@ This module defines the Link object used in Link extractors.
 For actual link extractors implementation see scrapy.linkextractors, or
 its documentation in: docs/topics/link-extractors.rst
 """
-from scrapy.utils.python import to_native_str
+import warnings
+import six
+
+from scrapy.utils.python import to_bytes
 
 
 class Link(object):
@@ -14,9 +17,13 @@ class Link(object):
 
     def __init__(self, url, text='', fragment='', nofollow=False):
         if not isinstance(url, str):
-            import warnings
-            warnings.warn("Link urls must be str objects.")
-            url = to_native_str(url)
+            if six.PY2:
+                warnings.warn("Link urls must be str objects. "
+                              "Assuming utf-8 encoding (which could be wrong)")
+                url = to_bytes(url, encoding='utf8')
+            else:
+                got = url.__class__.__name__
+                raise TypeError("Link urls must be str objects, got %s" % got)
         self.url = url
         self.text = text
         self.fragment = fragment
diff --git a/tests/test_link.py b/tests/test_link.py
index c8487698f..955430b37 100644
--- a/tests/test_link.py
+++ b/tests/test_link.py
@@ -16,44 +16,42 @@ class LinkTest(unittest.TestCase):
         self.assertNotEqual(hash(link1), hash(link2))
 
     def test_eq_and_hash(self):
-        l1 = Link(b"http://www.example.com")
-        l2 = Link(b"http://www.example.com/other")
-        l3 = Link(b"http://www.example.com")
+        l1 = Link("http://www.example.com")
+        l2 = Link("http://www.example.com/other")
+        l3 = Link("http://www.example.com")
 
         self._assert_same_links(l1, l1)
         self._assert_different_links(l1, l2)
         self._assert_same_links(l1, l3)
 
-        l4 = Link(b"http://www.example.com", text="test")
-        l5 = Link(b"http://www.example.com", text="test2")
-        l6 = Link(b"http://www.example.com", text="test")
+        l4 = Link("http://www.example.com", text="test")
+        l5 = Link("http://www.example.com", text="test2")
+        l6 = Link("http://www.example.com", text="test")
 
         self._assert_same_links(l4, l4)
         self._assert_different_links(l4, l5)
         self._assert_same_links(l4, l6)
 
-        l7 = Link(b"http://www.example.com", text="test", fragment='something', nofollow=False)
-        l8 = Link(b"http://www.example.com", text="test", fragment='something', nofollow=False)
-        l9 = Link(b"http://www.example.com", text="test", fragment='something', nofollow=True)
-        l10 = Link(b"http://www.example.com", text="test", fragment='other', nofollow=False)
+        l7 = Link("http://www.example.com", text="test", fragment='something', nofollow=False)
+        l8 = Link("http://www.example.com", text="test", fragment='something', nofollow=False)
+        l9 = Link("http://www.example.com", text="test", fragment='something', nofollow=True)
+        l10 = Link("http://www.example.com", text="test", fragment='other', nofollow=False)
         self._assert_same_links(l7, l8)
         self._assert_different_links(l7, l9)
         self._assert_different_links(l7, l10)
 
     def test_repr(self):
-        l1 = Link(b"http://www.example.com", text="test", fragment='something', nofollow=True)
+        l1 = Link("http://www.example.com", text="test", fragment='something', nofollow=True)
         l2 = eval(repr(l1))
         self._assert_same_links(l1, l2)
 
-    def test_non_str_url(self):
-        with warnings.catch_warnings(record=True) as w:
-            if six.PY2:
+    def test_non_str_url_py2(self):
+        if six.PY2:
+            with warnings.catch_warnings(record=True) as w:
                 link = Link(u"http://www.example.com/\xa3")
                 self.assertIsInstance(link.url, str)
                 self.assertEqual(link.url, b'http://www.example.com/\xc2\xa3')
-            else:
-                link = Link(b"http://www.example.com/\xc2\xa3")
-                self.assertIsInstance(link.url, str)
-                self.assertEqual(link.url, u'http://www.example.com/\xa3')
-
-        assert len(w) == 1, "warning not issued"
+            assert len(w) == 1, "warning not issued"
+        else:
+            with self.assertRaises(TypeError):
+                Link(b"http://www.example.com/\xc2\xa3")