diff --git a/src/python/mpsse.py b/src/python/mpsse.py
index 1774901..8130c85 100644
--- a/src/python/mpsse.py
+++ b/src/python/mpsse.py
@@ -97,8 +97,8 @@ def _ctypes_init(self):
 		self.libmpsse.MPSSE.restype = ctypes.c_void_p
 		self.libmpsse.OpenIndex.restype = ctypes.c_void_p
 
-		self.libmpsse.Read = ctypes.c_char_p
-		self.libmpsse.Transfer = ctypes.c_char_p
+		self.libmpsse.Read.restype = ctypes.c_char_p
+		self.libmpsse.Transfer.restype = ctypes.c_char_p
 		self.libmpsse.ErrorString.restype = ctypes.c_char_p
 		self.libmpsse.GetDescription.restype = ctypes.c_char_p