diff --git a/Lib/test/support/singlephase_helper.py b/Lib/test/support/singlephase_helper.py
new file mode 100644
index 00000000000000..7f827237cd8c8b
--- /dev/null
+++ b/Lib/test/support/singlephase_helper.py
@@ -0,0 +1,32 @@
+"""Helper module for _testembed.c test_subinterpreter_finalize test.
+"""
+
+import sys
+
+PREFIX = "shared_string_"
+SUFFIX = "DByGMRJRSEDp29PkiZQNHA"
+
+def init_sub1():
+    import _testsinglephase
+    # Create global object to be shared when imported a second time.
+    _testsinglephase._shared_list = []
+    # Create a new interned string, to be shared with the main interpreter.
+    _testsinglephase._shared_string = sys.intern(PREFIX + SUFFIX)
+
+
+def init_sub2():
+    # This sub-interpreter will share a reference to _shared_list with the
+    # first interpreter, since importing _testsinglephase will not initialize
+    # the module a second time but will just copy the global dict.  This
+    # situtation used to trigger a bug like gh-125286 if TraceRefs was enabled
+    # for the build.
+    import _testsinglephase
+
+
+def init_main():
+    global shared_str
+    # The first sub-interpreter has already interned this string value.  The
+    # return value from intern() will be the same string object created in
+    # sub-interpreter 1.  Assign it to a global so it lives until the main
+    # interpreter is shutdown.
+    shared_string = sys.intern(PREFIX + SUFFIX)
diff --git a/Programs/_testembed.c b/Programs/_testembed.c
index ab619e32429d63..e4c385720de6f2 100644
--- a/Programs/_testembed.c
+++ b/Programs/_testembed.c
@@ -2072,6 +2072,46 @@ static void configure_init_main(PyConfig *config)
 }
 
 
+static int test_subinterpreter_finalize(void)
+{
+    // This test is done by creating two subinterpreters and then sharing
+    // objects between them by importing a basic single-phase init extension
+    // (m_size == -1). Then we finalize the interpreters in the reverse order
+    // so that the interpreter that created the shared objects gets finalized
+    // first.
+    _testembed_Py_InitializeFromConfig();
+
+    PyThreadState *tstate1 = Py_NewInterpreter();
+    PyThreadState_Swap(tstate1);
+    PyRun_SimpleString(
+        "import test.support.singlephase_helper\n"
+        "test.support.singlephase_helper.init_sub1\n"
+    );
+
+    PyThreadState *tstate2 = Py_NewInterpreter();
+    PyThreadState_Swap(tstate2);
+    PyRun_SimpleString(
+        "import test.support.singlephase_helper\n"
+        "test.support.singlephase_helper.init_sub2\n"
+    );
+
+    PyThreadState *main_tstate = _PyRuntime.main_tstate;
+    PyThreadState_Swap(main_tstate);
+    PyRun_SimpleString(
+        "import test.support.singlephase_helper\n"
+        "test.support.singlephase_helper.init_main\n"
+    );
+
+    PyThreadState_Swap(tstate1);
+    Py_EndInterpreter(tstate1);
+    PyThreadState_Swap(tstate2);
+    Py_EndInterpreter(tstate2);
+    Py_Finalize();
+
+    return 0;
+}
+
+
 static int test_init_run_main(void)
 {
     PyConfig config;
@@ -2480,6 +2520,7 @@ static struct TestCase TestCases[] = {
     {"test_initconfig_get_api", test_initconfig_get_api},
     {"test_initconfig_exit", test_initconfig_exit},
     {"test_initconfig_module", test_initconfig_module},
+    {"test_subinterpreter_finalize", test_subinterpreter_finalize},
     {"test_run_main", test_run_main},
     {"test_run_main_loop", test_run_main_loop},
     {"test_get_argc_argv", test_get_argc_argv},