diff --git a/src/_wrappers.c b/src/_wrappers.c
index 2deb6d0..1661c42 100644
--- a/src/_wrappers.c
+++ b/src/_wrappers.c
@@ -2044,6 +2044,16 @@ moduleinit(void)
     PyModule_AddObject(module, "FunctionWrapper",
             (PyObject *)&WraptFunctionWrapper_Type);
 
+    Py_INCREF(&WraptFunctionWrapperBase_Type);
+    PyModule_AddObject(module, "_FunctionWrapperBase",
+            (PyObject *)&WraptFunctionWrapperBase_Type);
+    Py_INCREF(&WraptBoundFunctionWrapper_Type);
+    PyModule_AddObject(module, "_BoundFunctionWrapper",
+            (PyObject *)&WraptBoundFunctionWrapper_Type);
+    Py_INCREF(&WraptBoundMethodWrapper_Type);
+    PyModule_AddObject(module, "_BoundMethodWrapper",
+            (PyObject *)&WraptBoundMethodWrapper_Type);
+
     return module;
 }
 
diff --git a/src/wrappers.py b/src/wrappers.py
index 2ead039..475c94c 100644
--- a/src/wrappers.py
+++ b/src/wrappers.py
@@ -509,7 +509,8 @@ class FunctionWrapper(_FunctionWrapperBase):
                 adapter, bound_type)
 
 try:
-    from ._wrappers import ObjectProxy, FunctionWrapper
+    from ._wrappers import (ObjectProxy, FunctionWrapper,
+            _FunctionWrapperBase, _BoundFunctionWrapper, _BoundMethodWrapper)
 except ImportError:
     pass