diff --git a/src/ChangeLog b/src/ChangeLog
index 07152a57..45b2a70a 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2012-11-24  Gijs van Tulder  <gvtulder@gmail.com>
+
+	* warc.c (warc_write_cdx_record): Use `number_to_string' to
+	convert the offset to a string.
+
 2012-11-24  Giuseppe Scrivano  <gscrivano@gnu.org>
 
 	* warc.c (warc_write_block_from_file): Use `number_to_string' to
diff --git a/src/warc.c b/src/warc.c
index 99e70166..25a8517f 100644
--- a/src/warc.c
+++ b/src/warc.c
@@ -1225,10 +1225,14 @@ warc_write_cdx_record (const char *url, const char *timestamp_str,
   if (redirect_location == NULL || strlen(redirect_location) == 0)
     redirect_location = "-";
 
+  char offset_string[22];
+  number_to_string (offset_string, offset);
+
   /* Print the CDX line. */
-  fprintf (warc_current_cdx_file, "%s %s %s %s %d %s %s - %ld %s %s\n", url,
+  fprintf (warc_current_cdx_file, "%s %s %s %s %d %s %s - %s %s %s\n", url,
            timestamp_str_cdx, url, mime_type, response_code, checksum,
-           redirect_location, offset, warc_current_filename, response_uuid);
+           redirect_location, offset_string, warc_current_filename,
+           response_uuid);
   fflush (warc_current_cdx_file);
 
   return true;