diff --git a/src/cfgparse.c b/src/cfgparse.c
index d5a6f04f7..f7944c3aa 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -828,6 +828,11 @@ int cfg_parse_global(const char *file, int linenum, char **args, int kwm)
 			goto out;
 		}
 		global.tune.bufsize = atol(args[1]);
+		if (global.tune.bufsize <= 0) {
+			Alert("parsing [%s:%d] : '%s' expects a positive integer argument.\n", file, linenum, args[0]);
+			err_code |= ERR_ALERT | ERR_FATAL;
+			goto out;
+		}
 		if (global.tune.maxrewrite >= global.tune.bufsize / 2)
 			global.tune.maxrewrite = global.tune.bufsize / 2;
 		chunk_init(&trash, realloc(trash.str, global.tune.bufsize), global.tune.bufsize);