diff --git a/src/ChangeLog b/src/ChangeLog
index 0755541d..f374605a 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,10 @@
+2012-11-26  Giuseppe Scrivano  <gscrivano@gnu.org>
+
+	* wget.h (MAX_INT_TO_STRING_LEN): Define macro.
+	* warc.c (warc_write_block_from_file): Use `MAX_INT_TO_STRING_LEN'
+	to find the buffer size.
+	(warc_write_cdx_record): Likewise.
+
 2012-09-03  Tim Ruehsen  <tim.ruehsen@gmx.de>
 
 	* http.c (digest_authentication_encode): Add support for RFC 2617
diff --git a/src/warc.c b/src/warc.c
index 3203d4de..fb506a7f 100644
--- a/src/warc.c
+++ b/src/warc.c
@@ -245,7 +245,7 @@ static bool
 warc_write_block_from_file (FILE *data_in)
 {
   /* Add the Content-Length header. */
-  char content_length[22];
+  char content_length[MAX_INT_TO_STRING_LEN(off_t)];
   fseeko (data_in, 0L, SEEK_END);
   number_to_string (content_length, ftello (data_in));
   warc_write_header ("Content-Length", content_length);
@@ -1225,7 +1225,7 @@ 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];
+  char offset_string[MAX_INT_TO_STRING_LEN(off_t)];
   number_to_string (offset_string, offset);
 
   /* Print the CDX line. */
diff --git a/src/wget.h b/src/wget.h
index ca4a702d..14a1965e 100644
--- a/src/wget.h
+++ b/src/wget.h
@@ -314,6 +314,10 @@ typedef double SUM_SIZE_INT;
    0-pad the address.)  */
 #define PTR_FORMAT(p) (int) (2 * sizeof (void *)), (unsigned long) (p)
 
+/* Find the maximum buffer length needed to print an integer of type `x'
+   in base 10. 24082 / 10000 = 8*log_{10}(2).  */
+#define MAX_INT_TO_STRING_LEN(x) ((sizeof(x) * 24082 / 10000) + 2)
+
 extern const char *exec_name;
 
 /* Document type ("dt") flags */