@@ -52,7 +52,7 @@ def dumps(obj):
     """
     pickler = NumbaPickler
     with io.BytesIO() as buf:
-        p = pickler(buf)
+        p = pickler(buf, protocol=4)
         p.dump(obj)
         pickled = buf.getvalue()
 
 
@@ -6,13 +6,15 @@
 import operator
 import timeit
 import math
+import sys
 import traceback
 import weakref
 import warnings
 import threading
 import contextlib
 
 from types import ModuleType
+from importlib import import_module
 from collections.abc import Mapping, Sequence
 import numpy as np
 
@@ -537,3 +539,47 @@ def unified_function_type(numba_types, require_precise=True):
         function = types.UndefinedFunctionType(mnargs, dispatchers)
 
     return function
+
+
+class _RedirectSubpackage(ModuleType):
+    """Redirect a subpackage to a subpackage.
+
+    This allows all references like:
+
+    >>> from numba.old_subpackage import module
+    >>> module.item
+
+    >>> import numba.old_subpackage.module
+    >>> numba.old_subpackage.module.item
+
+    >>> from numba.old_subpackage.module import item
+    """
+    def __init__(self, old_module_locals, new_module):
+        old_module = old_module_locals['__name__']
+        super().__init__(old_module)
+
+        self.__old_module_states = {}
+        self.__new_module = new_module
+
+        new_mod_obj = import_module(new_module)
+
+        # Map all sub-modules over
+        for k, v in new_mod_obj.__dict__.items():
+            # Get attributes so that `subpackage.xyz` and
+            # `from subpackage import xyz` work
+            setattr(self, k, v)
+            if isinstance(v, ModuleType):
+                # Map modules into the interpreter so that
+                # `import subpackage.xyz` works
+                sys.modules[f"{old_module}.{k}"] = sys.modules[v.__name__]
+
+        # copy across dunders so that package imports work too
+        for attr, value in old_module_locals.items():
+            if attr.startswith('__') and attr.endswith('__'):
+                if attr != "__builtins__":
+                    setattr(self, attr, value)
+                    self.__old_module_states[attr] = value
+
+    def __reduce__(self):
+        args = (self.__old_module_states, self.__new_module)
+        return _RedirectSubpackage, args
@@ -1,9 +1,3 @@
-import importlib
-
-
-def __getattr__(name):
-    """Redirect to numba.core.types
-    """
-    # Uses PEP-562
-    basemod = importlib.import_module(f"numba.core.types", __name__)
-    return getattr(basemod, name)
+import sys
+from numba.core.utils import _RedirectSubpackage
+sys.modules[__name__] = _RedirectSubpackage(locals(), "numba.core.types")