diff --git a/mktree.c b/mktree.c
index 2e84889c02..bb23c4425b 100644
--- a/mktree.c
+++ b/mktree.c
@@ -61,6 +61,7 @@ static void write_tree(unsigned char *sha1)
 	}
 
 	write_sha1_file(buf.buf, buf.len, tree_type, sha1);
+	strbuf_release(&buf);
 }
 
 static const char mktree_usage[] = "git-mktree [-z]";