diff --git a/tests/fetchurl.sh b/tests/fetchurl.sh
index 7319ced2b..2535651b0 100644
--- a/tests/fetchurl.sh
+++ b/tests/fetchurl.sh
@@ -35,7 +35,7 @@ clearStore
 hash=$(nix hash-file --type sha512 --base64 ./fetchurl.sh)
 hash32=$(nix hash-file --type sha512 --base16 ./fetchurl.sh)
 
-mirror=$TMPDIR/hashed-mirror
+mirror=$TEST_ROOT/hashed-mirror
 rm -rf $mirror
 mkdir -p $mirror/sha512
 ln -s $(pwd)/fetchurl.sh $mirror/sha512/$hash32