diff --git a/strbuf.c b/strbuf.c
index 0510f76c24b3b3ce66baa0f05054d3f01b960b6e..4b9e30cadcd1ff45e7d4f23b210b22006445da91 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -44,7 +44,9 @@ void strbuf_release(struct strbuf *sb)
 
 char *strbuf_detach(struct strbuf *sb, size_t *sz)
 {
-	char *res = sb->alloc ? sb->buf : NULL;
+	char *res;
+	strbuf_grow(sb, 0);
+	res = sb->buf;
 	if (sz)
 		*sz = sb->len;
 	strbuf_init(sb, 0);