diff --git a/pyopencl/__init__.py b/pyopencl/__init__.py
index c285555e421c16290a31a08a8f30a4af2c682190..141a048f57f4743d57a799eb9aac0a2e41738879 100644
--- a/pyopencl/__init__.py
+++ b/pyopencl/__init__.py
@@ -514,17 +514,6 @@ def _add_functionality():
 
         self._arg_type_chars = arg_type_chars
 
-    _size_t_char = ({
-        8: 'Q',
-        4: 'L',
-        2: 'H',
-        1: 'B',
-        })[_cl._ffi.sizeof('size_t')]
-    _type_char_map = {
-        'n': _size_t_char.lower(),
-        'N': _size_t_char
-    }
-    del _size_t_char
     def kernel_set_args(self, *args):
         assert len(args) == self.num_args, (
                 "length of argument list (%d) and "
@@ -539,20 +528,14 @@ def _add_functionality():
                 for i, arg in enumerate(args):
                     self.set_arg(i, arg)
             else:
-                #from pyopencl._pvt_struct import pack
-                from struct import pack
+                from pyopencl._pvt_struct import pack
+
                 for i, (arg, arg_type_char) in enumerate(
                         zip(args, arg_type_chars)):
-                    if not arg_type_char or arg_type_char == "V":
-                        _arg = arg
-                    elif arg_type_char == "F":
-                        _arg = pack('f', arg.real) + pack('f', arg.imag)
-                    elif arg_type_char == "D":
-                        _arg = pack('d', arg.real) + pack('d', arg.imag)
+                    if arg_type_char and arg_type_char != "V":
+                        self.set_arg(i, pack(arg_type_char, arg))
                     else:
-                        _arg = pack(_type_char_map.get(arg_type_char,
-                                                       arg_type_char), arg)
-                    self.set_arg(i, _arg)
+                        self.set_arg(i, arg)
         except LogicError, e:
             if i is not None:
                 advice = ""
diff --git a/pyopencl/_pvt_struct.py b/pyopencl/_pvt_struct.py
new file mode 100644
index 0000000000000000000000000000000000000000..b29f31efbb30d546764b0b440cb29600596e9757
--- /dev/null
+++ b/pyopencl/_pvt_struct.py
@@ -0,0 +1,50 @@
+from __future__ import division
+
+__copyright__ = """
+Copyright (C) 2013 Marko Bencun
+Copyright (C) 2014 Andreas Kloeckner
+Copyright (C) 2014 Yichao Yu
+"""
+
+__license__ = """
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+"""
+
+#import pyopencl._cl as _cl
+import pyopencl.cffi_cl as _cl
+from struct import pack as _pack
+
+_size_t_char = ({
+    8: 'Q',
+    4: 'L',
+    2: 'H',
+    1: 'B',
+})[_cl._ffi.sizeof('size_t')]
+_type_char_map = {
+    'n': _size_t_char.lower(),
+    'N': _size_t_char
+}
+del _size_t_char
+def pack(type_char, obj):
+    if type_char == 'F':
+        return _pack('f', obj.real) + _pack('f', obj.imag)
+    elif type_char == "D":
+        return _pack('d', obj.real) + _pack('d', obj.imag)
+    else:
+        return _pack(_type_char_map.get(type_char, type_char), obj)