From ae465621ffe937dfc7b2a15df687143645b7dee5 Mon Sep 17 00:00:00 2001
From: Jan Tojnar <jtojnar@gmail.com>
Date: Wed, 20 Nov 2019 05:05:59 +0100
Subject: [PATCH] pythonPackages.pipBuildHook: fix unbound variable

for compatibility with set -u
---
 pkgs/development/interpreters/python/hooks/pip-build-hook.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pkgs/development/interpreters/python/hooks/pip-build-hook.sh b/pkgs/development/interpreters/python/hooks/pip-build-hook.sh
index a58c01ce808c..292f13d30154 100644
--- a/pkgs/development/interpreters/python/hooks/pip-build-hook.sh
+++ b/pkgs/development/interpreters/python/hooks/pip-build-hook.sh
@@ -36,7 +36,7 @@ if [ -z "${dontUsePipBuild-}" ] && [ -z "${buildPhase-}" ]; then
     buildPhase=pipBuildPhase
 fi
 
-if [ -z "$shellHook" ]; then
+if [ -z "${shellHook-}" ]; then
     echo "Using pipShellHook"
     shellHook=pipShellHook
 fi