1 files changed, 4 insertions, 3 deletions

diff --git a/strbuf.c b/strbuf.c
index dbd8c4bcfb..b9b194b320 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -118,12 +118,13 @@ void strbuf_addf(struct strbuf *sb, const char *fmt, ...)
 	int len;
 	va_list ap;
 
+	if (!strbuf_avail(sb))
+		strbuf_grow(sb, 64);
 	va_start(ap, fmt);
 	len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap);
 	va_end(ap);
-	if (len < 0) {
-		len = 0;
-	}
+	if (len < 0)
+		die("your vsnprintf is broken");
 	if (len > strbuf_avail(sb)) {
 		strbuf_grow(sb, len);
 		va_start(ap, fmt);