diff --git a/python/src/com/jetbrains/python/inspections/PyPep8NamingInspection.java b/python/src/com/jetbrains/python/inspections/PyPep8NamingInspection.java
index 9a584e0ffff4..1da2c46403e0 100644
--- a/python/src/com/jetbrains/python/inspections/PyPep8NamingInspection.java
+++ b/python/src/com/jetbrains/python/inspections/PyPep8NamingInspection.java
@@ -136,7 +136,7 @@ public class PyPep8NamingInspection extends PyInspection {
         return true;
       }
       for (PyClassLikeType ancestor : pyClass.getAncestorTypes(myTypeEvalContext)) {
-        if (blackList.contains(ancestor.getClassQName())) {
+        if (ancestor != null && blackList.contains(ancestor.getClassQName())) {
           return true;
         }
       }