diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index 1f596ada5a0b..7fe5f67b14de 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -1594,7 +1594,7 @@ genericBuild() {
 
         if [ "$curPhase" = unpackPhase ]; then
             # make sure we can cd into the directory
-            [ -z "${sourceRoot}" ] || chmod +x "${sourceRoot}"
+            [ -n "${sourceRoot:-}" ] && chmod +x "${sourceRoot}"
 
             cd "${sourceRoot:-.}"
         fi