Fix the builtin module initialization code to store the init function for future reinitialization.
diff --git a/Misc/NEWS b/Misc/NEWS
index b3c5b88..d6728be 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@
 Core and Builtins
 -----------------
 
+- Fix the builtin module initialization code to store the init function for
+  future reinitialization.
+
 - Issue #13629: Renumber the tokens in token.h so that they match the indexes
   into _PyParser_TokenNames.
 
diff --git a/Python/import.c b/Python/import.c
index e721498..ee3f9b0 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -2169,6 +2169,7 @@
 
     for (p = PyImport_Inittab; p->name != NULL; p++) {
         PyObject *mod;
+        PyModuleDef *def;
         if (strcmp(name, p->name) == 0) {
             if (p->initfunc == NULL) {
                 PyErr_Format(PyExc_ImportError,
@@ -2181,6 +2182,9 @@
             mod = (*p->initfunc)();
             if (mod == 0)
                 return -1;
+            /* Remember pointer to module init function. */
+            def = PyModule_GetDef(mod);
+            def->m_base.m_init = p->initfunc;
             if (_PyImport_FixupBuiltin(mod, name) < 0)
                 return -1;
             /* FixupExtension has put the module into sys.modules,