diff --git a/testing/root/test_builtin.py b/testing/root/test_builtin.py
index a47eacc4..287c60d5 100644
--- a/testing/root/test_builtin.py
+++ b/testing/root/test_builtin.py
@@ -93,7 +93,7 @@ class A:
 
 def test_getfuncdict():
     def f():
-        pass
+        raise NotImplementedError
     f.x = 4
     assert py.builtin._getfuncdict(f)["x"] == 4
     assert py.builtin._getfuncdict(2) is None
diff --git a/tox.ini b/tox.ini
index 45f22524..dd8828b2 100644
--- a/tox.ini
+++ b/tox.ini
@@ -39,3 +39,6 @@ source = .
 parallel = 1
 [coverage:report]
 include = py/*,testing/*
+exclude_lines =
+    #\s*(pragma|PRAGMA)[:\s]?\s*(no|NO)\s*(cover|COVER)
+    ^\s*raise NotImplementedError\b