diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
index 481de85fde..486412deec 100644
--- a/Modules/_ctypes/_ctypes.c
+++ b/Modules/_ctypes/_ctypes.c
@@ -3075,7 +3075,7 @@ int _ctypes_simple_instance(PyObject *obj)
     PyTypeObject *type = (PyTypeObject *)obj;
 
     if (PyCSimpleTypeObject_Check(type))
-        return type->tp_base != &Simple_Type;
+        return type->tp_base == &Simple_Type;
     return 0;
 }
 
@@ -3088,7 +3088,7 @@ PyCData_get(PyObject *type, GETFUNC getfunc, PyObject *src,
         return getfunc(adr, size);
     assert(type);
     dict = PyType_stgdict(type);
-    if (dict && dict->getfunc && !_ctypes_simple_instance(type))
+    if (dict && dict->getfunc && _ctypes_simple_instance(type))
         return dict->getfunc(adr, size);
     return PyCData_FromBaseObj(type, src, index, adr);
 }
@@ -5003,7 +5003,7 @@ static PyGetSetDef Simple_getsets[] = {
 static PyObject *
 Simple_from_outparm(PyObject *self, PyObject *args)
 {
-    if (_ctypes_simple_instance((PyObject *)Py_TYPE(self))) {
+    if (!_ctypes_simple_instance((PyObject *)Py_TYPE(self))) {
         Py_INCREF(self);
         return self;
     }
diff --git a/Modules/_ctypes/callbacks.c b/Modules/_ctypes/callbacks.c
index 591b944d76..75ef63b799 100644
--- a/Modules/_ctypes/callbacks.c
+++ b/Modules/_ctypes/callbacks.c
@@ -176,7 +176,7 @@ static void _CallPythonObject(void *mem,
         StgDictObject *dict;
         dict = PyType_stgdict(cnv);
 
-        if (dict && dict->getfunc && !_ctypes_simple_instance(cnv)) {
+        if (dict && dict->getfunc && _ctypes_simple_instance(cnv)) {
             PyObject *v = dict->getfunc(*pArgs, dict->size);
             if (!v) {
                 PrintError("create argument %zd:\n", i);
diff --git a/Modules/_ctypes/callproc.c b/Modules/_ctypes/callproc.c
index 4a6b8ec3ee..af4706d6ea 100644
--- a/Modules/_ctypes/callproc.c
+++ b/Modules/_ctypes/callproc.c
@@ -977,7 +977,7 @@ static PyObject *GetResult(PyObject *restype, void *result, PyObject *checker)
     if (dict == NULL)
         return PyObject_CallFunction(restype, "i", *(int *)result);
 
-    if (dict->getfunc && !_ctypes_simple_instance(restype)) {
+    if (dict->getfunc && _ctypes_simple_instance(restype)) {
         retval = dict->getfunc(result, dict->size);
         /* If restype is py_object (detected by comparing getfunc with
            O_get), we have to call Py_DECREF because O_get has already