diff --git a/builtin/commit.c b/builtin/commit.c
index 1c9e8e2..599fd10 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -534,7 +534,7 @@ static void export_one(const char *var, const char *s, const char *e, int hack)
 	struct strbuf buf = STRBUF_INIT;
 	if (hack)
 		strbuf_addch(&buf, hack);
-	strbuf_addf(&buf, "%.*s", (int)(e - s), s);
+	strbuf_add(&buf, s, e - s);
 	setenv(var, buf.buf, 1);
 	strbuf_release(&buf);
 }