diff --git a/fetch-pack.c b/fetch-pack.c
index 7f20eca4f8..289121038e 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -794,6 +794,10 @@ static void write_promisor_file(const char *keep_name,
 	strbuf_release(&promisor_name);
 }
 
+/*
+ * Pass 1 as "only_packfile" if the pack received is the only pack in this
+ * fetch request (that is, if there were no packfile URIs provided).
+ */
 static int get_pack(struct fetch_pack_args *args,
 		    int xd[2], struct string_list *pack_lockfiles,
 		    int only_packfile,