diff -Naur Python-2.7.9/Lib/ctypes/test/test_win32.py Python-2.7.9-mod/Lib/ctypes/test/test_win32.py
--- Python-2.7.9/Lib/ctypes/test/test_win32.py	Wed Dec 10 15:59:33 2014
+++ Python-2.7.9-mod/Lib/ctypes/test/test_win32.py	Wed Mar 25 12:10:48 2015
@@ -113,6 +113,48 @@
             self.assertEqual(ret.right, right.value)
             self.assertEqual(ret.top, top.value)
             self.assertEqual(ret.bottom, bottom.value)
+    def test_struct_callback(self):
+        class POINT(Structure):
+            _fields_ = [("x", c_long),
+                        ("y", c_long)]
+
+        class RECT(Structure):
+            _fields_ = [("left", c_long),
+                        ("top", c_long),
+                        ("right", c_long),
+                        ("bottom", c_long)]
+
+        dll = CDLL(_ctypes_test.__file__)
+
+        callback_RECT = CFUNCTYPE(c_int, RECT)
+        callback_POINT = CFUNCTYPE(c_int, POINT)
+
+        rect = RECT( 10,20,30,40 )
+        def check_RECT(cb_rect):
+            if cb_rect.left != rect.left: 
+                return 0
+            if cb_rect.top != rect.top: 
+                return 0
+            if cb_rect.right != rect.right: 
+                return 0
+            if cb_rect.bottom != rect.bottom: 
+                return 0
+            return 1
+        
+        result = dll.callback_RECT_test( rect, callback_RECT( check_RECT ))
+        self.assertEqual(result, 1)
+
+        point = POINT( 100,200 )
+        def check_POINT(cb_pt):
+            if cb_pt.x != point.x: 
+                return 0
+            if cb_pt.y != point.y: 
+                return 0
+            return 1
+        
+        result = dll.callback_POINT_test( point, callback_POINT( check_POINT ))
+        self.assertEqual(result, 1)
+        
 
 if __name__ == '__main__':
     unittest.main()
diff -Naur Python-2.7.9/Modules/_ctypes/_ctypes_test.c Python-2.7.9-mod/Modules/_ctypes/_ctypes_test.c
--- Python-2.7.9/Modules/_ctypes/_ctypes_test.c	Wed Dec 10 15:59:51 2014
+++ Python-2.7.9-mod/Modules/_ctypes/_ctypes_test.c	Wed Mar 25 12:14:51 2015
@@ -583,6 +583,18 @@
     return ar;
 }
 
+typedef int (*callback_RECT)(RECT r);
+typedef int (*callback_POINT)(POINT r);
+
+EXPORT(int) callback_RECT_test( RECT r, callback_RECT cb )
+{
+    return cb(r);
+}
+EXPORT(int) callback_POINT_test( POINT p, callback_POINT cb )
+{
+    return cb(p);
+}
+
 typedef struct {
     short x;
     short y;
diff -Naur Python-2.7.9/Modules/_ctypes/libffi_msvc/ffi.c Python-2.7.9-mod/Modules/_ctypes/libffi_msvc/ffi.c
--- Python-2.7.9/Modules/_ctypes/libffi_msvc/ffi.c	Wed Dec 10 15:59:52 2014
+++ Python-2.7.9-mod/Modules/_ctypes/libffi_msvc/ffi.c	Wed Mar 25 11:38:02 2015
@@ -377,7 +377,19 @@
 
       /* because we're little endian, this is what it turns into.   */
 
-      *p_argv = (void*) argp;
+#if _WIN64
+      if ((*p_arg)->type == FFI_TYPE_STRUCT && z > 8)
+        {
+          z = 8;
+          *p_argv = *(void**)argp;
+        }
+      else
+        {
+          *p_argv = (void*) argp;
+        }
+#else
+      *p_argv = (void*)argp;
+#endif
 
       p_argv++;
       argp += z;