diff --git a/tpl/strings/strings_test.go b/tpl/strings/strings_test.go
index f3bb82c63a1..d2bd9907704 100644
--- a/tpl/strings/strings_test.go
+++ b/tpl/strings/strings_test.go
@@ -451,9 +451,9 @@ func TestSubstr(t *testing.T) {
 		{"abcdef", -3, 1, "d"},
 		{"abcdef", 0, -1, "abcde"},
 		{"abcdef", 2, -1, "cde"},
-		{"abcdef", 4, -4, ""},
-		{"abcdef", 7, 1, ""},
-		{"abcdef", 6, nil, ""},
+		{"abcdef", 4, -4, false},
+		{"abcdef", 7, 1, false},
+		{"abcdef", 6, nil, false},
 		{"abcdef", 1, 100, "bcdef"},
 		{"abcdef", -100, 3, "abc"},
 		{"abcdef", -3, -1, "de"},