diff --git a/Lib/ctypes/test/test_as_parameter.py b/Lib/ctypes/test/test_as_parameter.py
index 5716f16..0581059 100644
--- a/Lib/ctypes/test/test_as_parameter.py
+++ b/Lib/ctypes/test/test_as_parameter.py
@@ -61,6 +61,7 @@
 
         def callback(v):
             args.append(v)
+            return v
 
         CallBack = CFUNCTYPE(c_int, c_int)
 
diff --git a/Lib/ctypes/test/test_functions.py b/Lib/ctypes/test/test_functions.py
index bfa0cad..759aea7 100644
--- a/Lib/ctypes/test/test_functions.py
+++ b/Lib/ctypes/test/test_functions.py
@@ -222,6 +222,7 @@
 
         def callback(v):
             args.append(v)
+            return v
 
         CallBack = CFUNCTYPE(c_int, c_int)
 
diff --git a/Misc/NEWS b/Misc/NEWS
index ab40d3d..dc99ff7 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -64,6 +64,11 @@
 Library
 -------
 
+- If a the Python part of a ctypes callback function returns None,
+  and this cannot be converted to the required C type, an exception is
+  printed with PyErr_WriteUnraisable.  Before this change, the C
+  callback did return arbitrary values to the calling code.
+
 - The __repr__ method of a NULL ctypes.py_object() no longer raises
   an exception.
 
diff --git a/Modules/_ctypes/callbacks.c b/Modules/_ctypes/callbacks.c
index cbe3d03..c8e669a 100644
--- a/Modules/_ctypes/callbacks.c
+++ b/Modules/_ctypes/callbacks.c
@@ -205,7 +205,7 @@
 
 	result = PyObject_CallObject(callable, arglist);
 	CHECK("'calling callback function'", result);
-	if ((restype != &ffi_type_void) && result && result != Py_None) {
+	if ((restype != &ffi_type_void) && result) {
 		PyObject *keep;
 		assert(setfunc);
 #ifdef WORDS_BIGENDIAN