diff --git a/CHANGES b/CHANGES
index 2e4cd7796..05a5874d6 100644
--- a/CHANGES
+++ b/CHANGES
@@ -30,6 +30,8 @@ Bugs fixed
 * #3952: apidoc: module header is too escaped
 * #4275: Formats accepted by sphinx.util.i18n.format_date are limited
 * #4493: recommonmark raises AttributeError if AutoStructify enabled
+* #4209: intersphinx: In link title, "v" should be optional if target has no
+  version
 
 Testing
 --------
diff --git a/sphinx/ext/intersphinx.py b/sphinx/ext/intersphinx.py
index b5b955ae8..7ec89ab7f 100644
--- a/sphinx/ext/intersphinx.py
+++ b/sphinx/ext/intersphinx.py
@@ -315,8 +315,11 @@ def missing_reference(app, env, node, contnode):
             if '://' not in uri and node.get('refdoc'):
                 # get correct path in case of subdirectories
                 uri = path.join(relative_path(node['refdoc'], '.'), uri)
-            newnode = nodes.reference('', '', internal=False, refuri=uri,
-                                      reftitle=_('(in %s v%s)') % (proj, version))
+            if version:
+                reftitle = _('(in %s v%s)') % (proj, version)
+            else:
+                reftitle = _('(in %s)') % (proj,)
+            newnode = nodes.reference('', '', internal=False, refuri=uri, reftitle=reftitle)
             if node.get('refexplicit'):
                 # use whatever title was given
                 newnode.append(contnode)
diff --git a/tests/test_ext_intersphinx.py b/tests/test_ext_intersphinx.py
index aef495d30..91e21187b 100644
--- a/tests/test_ext_intersphinx.py
+++ b/tests/test_ext_intersphinx.py
@@ -24,7 +24,7 @@ from sphinx.ext.intersphinx import (
     load_mappings, missing_reference, _strip_basic_auth,
     _get_safe_url, fetch_inventory, INVENTORY_FILENAME, debug
 )
-from test_util_inventory import inventory_v2
+from test_util_inventory import inventory_v2, inventory_v2_not_having_version
 
 
 def fake_node(domain, type, target, content, **attrs):
@@ -271,6 +271,25 @@ def test_missing_reference_jsdomain(tempdir, app, status, warning):
     assert rn.astext() == 'baz()'
 
 
+@pytest.mark.xfail(os.name != 'posix', reason="Path separator mismatch issue")
+def test_inventory_not_having_version(tempdir, app, status, warning):
+    inv_file = tempdir / 'inventory'
+    inv_file.write_bytes(inventory_v2_not_having_version)
+    app.config.intersphinx_mapping = {
+        'https://docs.python.org/': inv_file,
+    }
+    app.config.intersphinx_cache_limit = 0
+
+    # load the inventory and check if it's done correctly
+    load_mappings(app)
+
+    rn = reference_check(app, 'py', 'mod', 'module1', 'foo')
+    assert isinstance(rn, nodes.reference)
+    assert rn['refuri'] == 'https://docs.python.org/foo.html#module-module1'
+    assert rn['reftitle'] == '(in foo)'
+    assert rn[0].astext() == 'Long Module desc'
+
+
 def test_load_mappings_warnings(tempdir, app, status, warning):
     """
     load_mappings issues a warning if new-style mapping
diff --git a/tests/test_util_inventory.py b/tests/test_util_inventory.py
index 3829de9ef..3d6c9f402 100644
--- a/tests/test_util_inventory.py
+++ b/tests/test_util_inventory.py
@@ -50,6 +50,15 @@ foo.bar.qux js:data 1 index.html#foo.bar.qux -
 a term including:colon std:term -1 glossary.html#term-a-term-including-colon -
 '''.encode('utf-8'))
 
+inventory_v2_not_having_version = '''\
+# Sphinx inventory version 2
+# Project: foo
+# Version: 
+# The remainder of this file is compressed with zlib.
+'''.encode('utf-8') + zlib.compress('''\
+module1 py:module 0 foo.html#module-module1 Long Module desc
+'''.encode('utf-8'))
+
 
 def test_read_inventory_v1():
     f = BytesIO(inventory_v1)
@@ -76,3 +85,10 @@ def test_read_inventory_v2():
         '/util/glossary.html#term-a-term'
     assert invdata['std:term']['a term including:colon'][2] == \
         '/util/glossary.html#term-a-term-including-colon'
+
+
+def test_read_inventory_v2_not_having_version():
+    f = BytesIO(inventory_v2_not_having_version)
+    invdata = InventoryFile.load(f, '/util', posixpath.join)
+    assert invdata['py:module']['module1'] == \
+        ('foo', '', '/util/foo.html#module-module1', 'Long Module desc')