diff --git a/jaraco/collections.py b/jaraco/collections.py
index 3ab9dc9..6a6e342 100644
--- a/jaraco/collections.py
+++ b/jaraco/collections.py
@@ -4,6 +4,7 @@ import collections.abc
 import itertools
 import copy
 import functools
+import platform
 
 from jaraco.classes.properties import NonDataProperty
 import jaraco.text
@@ -592,9 +593,14 @@ class DictStack(list, collections.abc.Mapping):
         return list(set(itertools.chain.from_iterable(c.keys() for c in self)))
 
     def __getitem__(self, key):
-        for scope in reversed(self):
-            if key in scope:
-                return scope[key]
+        if 'PyPy' in platform.python_implementation():
+            for scope in reversed(list(self)):
+                if key in scope:
+                    return scope[key]
+        else:
+            for scope in reversed(self):
+                if key in scope:
+                    return scope[key]
         raise KeyError(key)
 
     push = list.append