diff --git a/t/lib-parallel-checkout.sh b/t/lib-parallel-checkout.sh
index acaee9cbb6..8324d6c96d 100644
--- a/t/lib-parallel-checkout.sh
+++ b/t/lib-parallel-checkout.sh
@@ -20,7 +20,7 @@ test_checkout_workers () {
 		BUG "too few arguments to test_checkout_workers"
 	fi &&
 
-	local expected_workers=$1 &&
+	local expected_workers="$1" &&
 	shift &&
 
 	local trace_file=trace-test-checkout-workers &&
diff --git a/t/t2400-worktree-add.sh b/t/t2400-worktree-add.sh
index c28c04133c..ba320dc417 100755
--- a/t/t2400-worktree-add.sh
+++ b/t/t2400-worktree-add.sh
@@ -427,7 +427,7 @@ test_expect_success '"add" worktree with orphan branch, lock, and reason' '
 # Note: Quoted arguments containing spaces are not supported.
 test_wt_add_orphan_hint () {
 	local context="$1" &&
-	local use_branch=$2 &&
+	local use_branch="$2" &&
 	shift 2 &&
 	local opts="$*" &&
 	test_expect_success "'worktree add' show orphan hint in bad/orphan HEAD w/ $context" '
diff --git a/t/t4210-log-i18n.sh b/t/t4210-log-i18n.sh
index d2dfcf164e..75216f19ce 100755
--- a/t/t4210-log-i18n.sh
+++ b/t/t4210-log-i18n.sh
@@ -64,7 +64,7 @@ test_expect_success 'log --grep does not find non-reencoded values (latin1)' '
 '
 
 triggers_undefined_behaviour () {
-	local engine=$1
+	local engine="$1"
 
 	case $engine in
 	fixed)
@@ -85,7 +85,7 @@ triggers_undefined_behaviour () {
 }
 
 mismatched_git_log () {
-	local pattern=$1
+	local pattern="$1"
 
 	LC_ALL=$is_IS_locale git log --encoding=ISO-8859-1 --format=%s \
 		--grep=$pattern
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 2eccf100c0..fc60708471 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -1765,7 +1765,7 @@ test_parse_ls_tree_oids () {
 # Choose a port number based on the test script's number and store it in
 # the given variable name, unless that variable already contains a number.
 test_set_port () {
-	local var=$1 port
+	local var="$1" port
 
 	if test $# -ne 1 || test -z "$var"
 	then