diff --git a/py_aax_decode/native.py b/py_aax_decode/native.py
index a41be0a..fd842f8 100644
--- a/py_aax_decode/native.py
+++ b/py_aax_decode/native.py
@@ -58,7 +58,7 @@ def main(in_file, out_file, dll_path=None):
 
 def open_file(dll, filename):
     handle = ctypes.pointer(ctypes.c_byte())
-    res = dll.AAXOpenFileWinW(handle, filename)
+    res = dll.AAXOpenFileWinW(byref(handle), filename)
 
     if res != 0:
         raise Exception('AAXOpenFileWinW: {}'.format(res))