diff --git a/parso/python/errors.py b/parso/python/errors.py
index db3a30f..5df4750 100644
--- a/parso/python/errors.py
+++ b/parso/python/errors.py
@@ -820,7 +820,10 @@ class _ArglistRule(SyntaxRule):
                         if first.type == 'name':
                             if first.value in arg_set:
                                 # f(x=1, x=2)
-                                self.add_issue(first, message="keyword argument repeated")
+                                message = "keyword argument repeated"
+                                if self._normalizer.version >= (3, 9):
+                                    message += ": {}".format(first.value)
+                                self.add_issue(first, message=message)
                             else:
                                 arg_set.add(first.value)
                 else:
diff --git a/test/test_python_errors.py b/test/test_python_errors.py
index 75ebb88..7131b1b 100644
--- a/test/test_python_errors.py
+++ b/test/test_python_errors.py
@@ -362,6 +362,16 @@ def test_continue_in_finally():
     ]
 )
 def test_forbidden_name(template, target):
-    assert _get_error_list(template.format(target=target), version="3")[0].message
+    assert _get_error_list(template.format(target=target), version="3")
 
 
+def test_repeated_kwarg():
+    # python 3.9+ shows which argument is repeated
+    assert (
+        _get_error_list("f(q=1, q=2)", version="3.8")[0].message
+        == "SyntaxError: keyword argument repeated"
+    )
+    assert (
+        _get_error_list("f(q=1, q=2)", version="3.9")[0].message
+        == "SyntaxError: keyword argument repeated: q"
+    )