From 43a523526dfe924e59b0eadf9319bb1a72fad743 Mon Sep 17 00:00:00 2001
From: Scott Olson <scott@solson.me>
Date: Fri, 19 Feb 2016 03:13:10 -0600
Subject: [PATCH] Require at least one of url or urls in fetchurl.

---
 pkgs/build-support/fetchurl/default.nix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkgs/build-support/fetchurl/default.nix b/pkgs/build-support/fetchurl/default.nix
index 2c802bb3679c..d4b46cf9e9d4 100644
--- a/pkgs/build-support/fetchurl/default.nix
+++ b/pkgs/build-support/fetchurl/default.nix
@@ -85,7 +85,7 @@ in
 }:
 
 assert builtins.isList urls;
-assert urls == [] || url == "";
+assert (urls == []) != (url == "");
 
 
 let