diff --git a/tests/scripts/thread-cert/common.py b/tests/scripts/thread-cert/common.py
index c69a9a46d..c82d6e706 100644
--- a/tests/scripts/thread-cert/common.py
+++ b/tests/scripts/thread-cert/common.py
@@ -39,7 +39,7 @@ pp_map = {1: 1, 0: 0, 3: -1, 2: -2}
 
 
 # Get the signed parent priority from the byte that parent priority is in.
-def map_pp(self, pp_byte):
+def map_pp(pp_byte):
     return pp_map[((pp_byte & 0xC0) >> 6)]
 
 
diff --git a/tests/scripts/thread-cert/mle.py b/tests/scripts/thread-cert/mle.py
index 5e9784103..e075be141 100644
--- a/tests/scripts/thread-cert/mle.py
+++ b/tests/scripts/thread-cert/mle.py
@@ -599,7 +599,7 @@ class Connectivity(object):
 
     @property
     def pp(self):
-        return common.map_pp(self, self._pp_byte)
+        return common.map_pp(self._pp_byte)
 
     @property
     def link_quality_3(self):
diff --git a/tests/scripts/thread-cert/test_mle.py b/tests/scripts/thread-cert/test_mle.py
index d577fad74..59afd7d93 100755
--- a/tests/scripts/thread-cert/test_mle.py
+++ b/tests/scripts/thread-cert/test_mle.py
@@ -1130,7 +1130,7 @@ class TestConnectivity(unittest.TestCase):
         actual_pp = connectivity_obj.pp
 
         # THEN
-        self.assertEqual(common.map_pp(self, pp_byte), actual_pp)
+        self.assertEqual(common.map_pp(pp_byte), actual_pp)
 
     def test_should_return_link_quality_3_value_when_link_quality_3_property_is_called(
         self):
@@ -1317,7 +1317,7 @@ class TestConnectivityFactory(unittest.TestCase):
 
         # THEN
         self.assertTrue(isinstance(actual_connectivity, mle.Connectivity))
-        self.assertEqual(common.map_pp(self, pp_byte), actual_connectivity.pp)
+        self.assertEqual(common.map_pp(pp_byte), actual_connectivity.pp)
         self.assertEqual(link_quality_3, actual_connectivity.link_quality_3)
         self.assertEqual(link_quality_2, actual_connectivity.link_quality_2)
         self.assertEqual(link_quality_1, actual_connectivity.link_quality_1)
@@ -1353,7 +1353,7 @@ class TestConnectivityFactory(unittest.TestCase):
 
         # THEN
         self.assertTrue(isinstance(actual_connectivity, mle.Connectivity))
-        self.assertEqual(common.map_pp(self, pp_byte), actual_connectivity.pp)
+        self.assertEqual(common.map_pp(pp_byte), actual_connectivity.pp)
         self.assertEqual(link_quality_3, actual_connectivity.link_quality_3)
         self.assertEqual(link_quality_2, actual_connectivity.link_quality_2)
         self.assertEqual(link_quality_1, actual_connectivity.link_quality_1)