diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index f8648d2..c0b59c0 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -22,6 +22,12 @@
 #define PyTuple_MAXFREELIST  2000  /* Maximum number of tuples of each size to save */
 #endif
 
+/* bpo-40521: tuple free lists are shared by all interpreters. */
+#ifdef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
+#  undef PyTuple_MAXSAVESIZE
+#  define PyTuple_MAXSAVESIZE 0
+#endif
+
 #if PyTuple_MAXSAVESIZE > 0
 /* Entries 1 up to PyTuple_MAXSAVESIZE are free lists, entry 0 is the empty
    tuple () of which at most one instance will be allocated.
@@ -248,7 +254,9 @@
 #endif
     }
     Py_TYPE(op)->tp_free((PyObject *)op);
+#if PyTuple_MAXSAVESIZE > 0
 done:
+#endif
     Py_TRASHCAN_END
 }