diff --git a/.coveragerc b/.coveragerc
index 9b2a819e3..7f6f849cd 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -22,6 +22,7 @@ exclude_lines =
     # Don't complain if tests don't hit defensive assertion code:
     raise AssertionError
     raise NotImplementedError
+    return NotImplemented
 
     # Don't complain if non-runnable code isn't run:
     if 0: