diff --git a/new_packet.pxd b/new_packet.pxd
index 4b749c1..6a79aee 100644
--- a/new_packet.pxd
+++ b/new_packet.pxd
@@ -191,7 +191,7 @@ cdef class CPacket:
     cdef timeval timestamp
     cdef u_int8_t hw_addr[8]
 
-    cdef nf_callback(self, nfq_q_handle *qh, nfgenmsg *nfmsg, nfq_data *nfa, void *data)
+    cdef int nf_callback(self, nfq_q_handle *qh, nfgenmsg *nfmsg, nfq_data *nfa, void *data)
     cdef parse(self, nfq_q_handle *qh, nfq_data *nfa) nogil
     cdef _parse(self)
     cdef void verdict(self, u_int32_t verdict)
diff --git a/new_packet.pyx b/new_packet.pyx
index d2ba92f..d9270ff 100644
--- a/new_packet.pyx
+++ b/new_packet.pyx
@@ -58,7 +58,7 @@ cdef class CPacket:
 
         '''Assign a packet from NFQ to this object. Parse the header and load local values.'''
 
-        cdef readonly unsigned char *data
+        cdef unsigned char *data
 
         self._qh = qh
         self._nfa = nfa