diff --git a/Lib/test/libregrtest/refleak.py b/Lib/test/libregrtest/refleak.py
index 25e71305402..20b05954c76 100644
--- a/Lib/test/libregrtest/refleak.py
+++ b/Lib/test/libregrtest/refleak.py
@@ -246,9 +246,13 @@ def dash_R_cleanup(fs, ps, pic, zdc, abcs):
     abs_classes = filter(isabstract, abs_classes)
     for abc in abs_classes:
         for obj in abc.__subclasses__() + [abc]:
-            for ref in abcs.get(obj, set()):
-                if ref() is not None:
-                    obj.register(ref())
+            refs = abcs.get(obj, None)
+            if refs is not None:
+                obj._abc_registry_clear()
+                for ref in refs:
+                    subclass = ref()
+                    if subclass is not None:
+                        obj.register(subclass)
             obj._abc_caches_clear()
 
     # Clear caches