diff --git a/tests/functional/ca/derivation-json.sh b/tests/functional/ca/derivation-json.sh
index c1480fd17..1e2a8fe35 100644
--- a/tests/functional/ca/derivation-json.sh
+++ b/tests/functional/ca/derivation-json.sh
@@ -1,29 +1,31 @@
+#!/usr/bin/env bash
+#
 source common.sh
 
 export NIX_TESTS_CA_BY_DEFAULT=1
 
 drvPath=$(nix-instantiate ../simple.nix)
 
-nix derivation show $drvPath | jq .[] > $TEST_HOME/simple.json
+nix derivation show "$drvPath" | jq .[] > "$TEST_HOME"/simple.json
 
-drvPath2=$(nix derivation add < $TEST_HOME/simple.json)
+drvPath2=$(nix derivation add < "$TEST_HOME"/simple.json)
 
 [[ "$drvPath" = "$drvPath2" ]]
 
 # Content-addressed derivations can be renamed.
-jq '.name = "foo"' < $TEST_HOME/simple.json > $TEST_HOME/foo.json
-drvPath3=$(nix derivation add --dry-run < $TEST_HOME/foo.json)
+jq '.name = "foo"' < "$TEST_HOME"/simple.json > "$TEST_HOME"/foo.json
+drvPath3=$(nix derivation add --dry-run < "$TEST_HOME"/foo.json)
 # With --dry-run nothing is actually written
 [[ ! -e "$drvPath3" ]]
 
 # But the JSON is rejected without the experimental feature
-expectStderr 1 nix derivation add < $TEST_HOME/foo.json --experimental-features nix-command | grepQuiet "experimental Nix feature 'ca-derivations' is disabled"
+expectStderr 1 nix derivation add < "$TEST_HOME"/foo.json --experimental-features nix-command | grepQuiet "experimental Nix feature 'ca-derivations' is disabled"
 
 # Without --dry-run it is actually written
-drvPath4=$(nix derivation add < $TEST_HOME/foo.json)
+drvPath4=$(nix derivation add < "$TEST_HOME"/foo.json)
 [[ "$drvPath4" = "$drvPath3" ]]
 [[ -e "$drvPath3" ]]
 
 # The modified derivation read back as JSON matches
-nix derivation show $drvPath3 | jq .[] > $TEST_HOME/foo-read.json
-diff $TEST_HOME/foo.json $TEST_HOME/foo-read.json
+nix derivation show "$drvPath3" | jq .[] > "$TEST_HOME"/foo-read.json
+diff "$TEST_HOME"/foo.json "$TEST_HOME"/foo-read.json