diff --git a/src/FqAuxBackend.h b/src/FqAuxBackend.h
index a09a372848c4217f9629916111e7b36cfab5d9b2..021b865db01f0b11d3b336d2bace901fa42046cb 100644
--- a/src/FqAuxBackend.h
+++ b/src/FqAuxBackend.h
@@ -14,7 +14,7 @@
 
 
 class FqAuxBackend:public FqBaseBackend {
-    unsigned long cur_offset;
+	off_t cur_offset;
     T_buf_info buf_info;
 
     void readBuffer();
diff --git a/src/FqMainBackend.cpp b/src/FqMainBackend.cpp
index c8cda45a566849523eb69ea9af5ed50204eeae94..21d56807a5db168599520970e65680448127f5a4 100644
--- a/src/FqMainBackend.cpp
+++ b/src/FqMainBackend.cpp
@@ -39,7 +39,7 @@
 
 #define _FILE_OFFSET_BITS 64 // for portability reasons on 32bits systems.
 
-//#define DEBUG
+#define DEBUG
 
 #ifdef DEBUG
 #include <string.h>
@@ -62,7 +62,7 @@ FqMainBackend::FqMainBackend(srp * io_sr):FqBaseBackend() {
 void FqMainBackend::processFile(char * filename,unsigned char f_id) {
     FILE * fp;
     int nread;
-    long cur_offset;
+    off_t cur_offset;
     mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
     this->i_filename=filename;
     this->f_id=f_id;
@@ -93,6 +93,7 @@ void FqMainBackend::processFile(char * filename,unsigned char f_id) {
 
 
 void FqMainBackend::onEndFastqRecord(T_fq_rec_info& rec_info,const T_buf_info& bufinfo) {
+	cout<<"finished processing read at iffset:"<<rec_info.rstart_offset<<endl;
     rpos rp=init_rpos(f_id,rec_info.rstart_offset);
     rinfo pe2info;
     int nb_k_mer_PE2;