diff --git a/ares/ares__read_line.c b/ares/ares__read_line.c
index d816f18c06de47b8f70f768d1776a7af99ff4b14..f550a7ad4816f5e9f23f2d8df3c34ccb9a50579a 100644
--- a/ares/ares__read_line.c
+++ b/ares/ares__read_line.c
@@ -30,7 +30,7 @@
 int ares__read_line(FILE *fp, char **buf, int *bufsize)
 {
   char *newbuf;
-  int offset = 0;
+  size_t offset = 0;
   size_t len;
 
   if (*buf == NULL)