diff --git a/test/completion/classes.py b/test/completion/classes.py
index 44967f6a..f9c9231b 100644
--- a/test/completion/classes.py
+++ b/test/completion/classes.py
@@ -179,6 +179,18 @@ SubClass.var
 #? ['class_sub', 'class_super']
 SubClass.class_
 
+# -----------------
+# inheritance of builtins
+# -----------------
+
+class Base(str):
+    pass
+
+#? ['upper']
+Base.upper
+#? ['upper']
+Base().upper
+
 # -----------------
 # __call__
 # -----------------