diff --git a/src/_pytest/python.py b/src/_pytest/python.py
index 9d6e23840..051650272 100644
--- a/src/_pytest/python.py
+++ b/src/_pytest/python.py
@@ -1158,7 +1158,7 @@ def _find_parametrized_scope(argnames, arg2fixturedefs, indirect):
     return "function"
 
 
-def _idval(val, argname, idx, idfn, item, config=None):
+def _idval(val, argname, idx, idfn, item, config):
     if idfn:
         s = None
         try:
@@ -1195,7 +1195,7 @@ def _idval(val, argname, idx, idfn, item, config=None):
     return str(argname) + str(idx)
 
 
-def _idvalset(idx, parameterset, argnames, idfn, ids, config=None, item=None):
+def _idvalset(idx, parameterset, argnames, idfn, ids, item, config):
     if parameterset.id is not None:
         return parameterset.id
     if ids is None or (idx >= len(ids) or ids[idx] is None):
@@ -1210,7 +1210,7 @@ def _idvalset(idx, parameterset, argnames, idfn, ids, config=None, item=None):
 
 def idmaker(argnames, parametersets, idfn=None, ids=None, config=None, item=None):
     ids = [
-        _idvalset(valindex, parameterset, argnames, idfn, ids, config, item)
+        _idvalset(valindex, parameterset, argnames, idfn, ids, config=config, item=item)
         for valindex, parameterset in enumerate(parametersets)
     ]
     if len(set(ids)) != len(ids):
diff --git a/testing/python/metafunc.py b/testing/python/metafunc.py
index e1dfb6d8b..b8cd68b11 100644
--- a/testing/python/metafunc.py
+++ b/testing/python/metafunc.py
@@ -244,7 +244,7 @@ class TestMetafunc(object):
             ),
         ]
         for val, expected in values:
-            assert _idval(val, "a", 6, None, item=None) == expected
+            assert _idval(val, "a", 6, None, item=None, config=None) == expected
 
     def test_bytes_idval(self):
         """unittest for the expected behavior to obtain ids for parametrized
@@ -278,7 +278,7 @@ class TestMetafunc(object):
 
         values = [(TestClass, "TestClass"), (test_function, "test_function")]
         for val, expected in values:
-            assert _idval(val, "a", 6, None, item=None) == expected
+            assert _idval(val, "a", 6, None, item=None, config=None) == expected
 
     @pytest.mark.issue250
     def test_idmaker_autoname(self):