diff --git a/pybass_constants.py b/pybass_constants.py
index 2980984..b503cf5 100644
--- a/pybass_constants.py
+++ b/pybass_constants.py
@@ -58,6 +58,11 @@ import sys, ctypes, platform
 if sys.hexversion < 0x02060000:
 	ctypes.c_bool = ctypes.c_byte
 
+if platform.system().lower() == 'windows':
+	func_type = ctypes.WINFUNCTYPE
+else:
+	func_type = ctypes.CFUNCTYPE
+
 QWORD = ctypes.c_int64
 
 def LOBYTE(a): return (ctypes.c_byte)(a)
@@ -516,7 +521,7 @@ BASS_FILEPOS_CONNECTED = 4
 BASS_FILEPOS_BUFFER = 5
 BASS_FILEPOS_SOCKET = 6
 
-DOWNLOADPROC = ctypes.CFUNCTYPE(ctypes.c_void_p, ctypes.c_void_p, ctypes.c_ulong, ctypes.c_void_p)
+DOWNLOADPROC = func_type(ctypes.c_void_p, ctypes.c_void_p, ctypes.c_ulong, ctypes.c_void_p)
 
 # BASS_ChannelSetSync types
 BASS_SYNC_POS = 0