From 96c158d6e1c6c3bed6451a3c6447d2b0bd0337ad Mon Sep 17 00:00:00 2001
From: Matthew Bauer <mjbauer95@gmail.com>
Date: Thu, 6 Aug 2020 19:00:33 -0500
Subject: [PATCH] Fix build

---
 src/libstore/builtins/fetchurl.cc | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/libstore/builtins/fetchurl.cc b/src/libstore/builtins/fetchurl.cc
index 2048f8f87..4fb5d8a06 100644
--- a/src/libstore/builtins/fetchurl.cc
+++ b/src/libstore/builtins/fetchurl.cc
@@ -63,8 +63,8 @@ void builtinFetchurl(const BasicDerivation & drv, const std::string & netrcData)
         for (auto hashedMirror : settings.hashedMirrors.get())
             try {
                 if (!hasSuffix(hashedMirror, "/")) hashedMirror += '/';
-                auto ht = parseHashType(getAttr("outputHashAlgo"));
-                auto h = Hash(getAttr("outputHash"), ht);
+                std::optional<HashType> ht = parseHashTypeOpt(getAttr("outputHashAlgo"));
+                Hash h = newHashAllowEmpty(getAttr("outputHash"), ht);
                 fetch(hashedMirror + printHashType(h.type) + "/" + h.to_string(Base16, false));
                 return;
             } catch (Error & e) {