diff --git a/pynetfilter_conntrack/conntrack.py b/pynetfilter_conntrack/conntrack.py
index b891555..7c2605c 100644
--- a/pynetfilter_conntrack/conntrack.py
+++ b/pynetfilter_conntrack/conntrack.py
@@ -24,9 +24,14 @@ def register_callback(self, callback, event_type=NFCT_T_ALL, data=None):
         return: NFCT_CB_CONTINUE, NFCT_CB_FAILURE, NFCT_CB_STOP,
         or NFCT_CB_STOLEN (like continue, but ct is not freed).
         """
+	self.event_type = event_type
         self.callback = nfct_callback_t(callback)
         self.callback_arg = data
-        nfct_callback_register(self.handle, event_type, self.callback, self.callback_arg)
+        ret = nfct_callback_register(self.handle, self.event_type, self.callback, self.callback_arg)
+        if ret == -1:
+            self._error('nfct_callback_register')
+        elif ret != 0:
+            self._error('nfct_callback_register unknown return code')
 
     def unregister_callback(self):
         """Unregister callback"""
@@ -90,9 +95,13 @@ def query(self, command, argument):
 
         May raise a RuntimeError.
         """
-        ret = nfct_query(self.handle, command, argument)
-        if ret != 0:
+	self.query_type = command
+
+        ret = nfct_query(self.handle, self.query_type, byref(argument))
+        if ret == -1:
             self._error('nfct_query')
+        elif ret != 0:
+            self._error('nfct_query unknown return code')
 
     def catch(self, callback):
         """
diff --git a/pynetfilter_conntrack/conntrack_base.py b/pynetfilter_conntrack/conntrack_base.py
index 36866b9..6b7494f 100644
--- a/pynetfilter_conntrack/conntrack_base.py
+++ b/pynetfilter_conntrack/conntrack_base.py
@@ -16,9 +16,12 @@ def __init__(self, subsys, subscriptions):
         self.conntrack = None
         self.handle = None
 
+	self.subsys = subsys
+	self.subscriptions = subscriptions
+
         # Open a conntrack handler
-        self.handle = nfct_open(subsys, subscriptions)
-        if not self.handle:
+        self.handle = nfct_open(self.subsys, self.subscriptions)
+        if self.handle == None:
             self._error('nfct_new')
 
     def _error(self, func_name):
diff --git a/pynetfilter_conntrack/func.py b/pynetfilter_conntrack/func.py
index b95d51a..6dff089 100644
--- a/pynetfilter_conntrack/func.py
+++ b/pynetfilter_conntrack/func.py
@@ -15,8 +15,10 @@
 #
 #nf_conntrack_p = POINTER(nf_conntrack)
 #nfct_handle_p = POINTER(nfct_handle)
-nf_conntrack_p = c_int
-nfct_handle_p = c_int
+#nf_conntrack_p = c_int
+#nfct_handle_p = c_int
+nf_conntrack_p = c_void_p
+nfct_handle_p = c_void_p
 
 class nfct_conntrack_compare_t(Structure):
     _fields_ = (
@@ -33,7 +35,7 @@ class nfct_conntrack_compare_t(Structure):
 #              void *data)
 #
 # Callback type
-nfct_callback_t = CFUNCTYPE(c_int, c_int, nf_conntrack_p, c_void_p)
+nfct_callback_t = CFUNCTYPE(c_int, c_uint, nf_conntrack_p, c_void_p)
 
 #--------------------------------------------------------------------------
 # struct nf_conntrack *nfct_new(void): Allocate a new conntrack
@@ -81,7 +83,7 @@ class nfct_conntrack_compare_t(Structure):
 # On error, -1 is returned and errno is explicitely set. On success, 0
 # is returned
 nfct_query = library.nfct_query
-nfct_query.argtypes = (nfct_handle_p, c_int, c_void_p)
+nfct_query.argtypes = (nfct_handle_p, c_uint, c_void_p)
 nfct_query.restype = c_int
 
 #--------------------------------------------------------------------------
@@ -93,7 +95,7 @@ class nfct_conntrack_compare_t(Structure):
 #				             void *data);
 # Register callback.
 nfct_callback_register = library.nfct_callback_register
-nfct_callback_register.argtypes = (nfct_handle_p, c_int, nfct_callback_t, c_void_p)
+nfct_callback_register.argtypes = (nfct_handle_p, c_uint, nfct_callback_t, c_void_p)
 nfct_callback_register.restype = c_int
 
 #--------------------------------------------------------------------------