diff --git a/tests/test_substitution.c b/tests/test_substitution.c
index b335d50ba..cb3161691 100644
--- a/tests/test_substitution.c
+++ b/tests/test_substitution.c
@@ -261,8 +261,8 @@ AST_TEST_DEFINE(test_substitution)
 	TEST(test_expected_result(test, c, "A${${baz}o:-2:-1}A", "A2A"));
 	pbx_builtin_setvar_helper(c, "list1", "ab&cd&ef");
 	TEST(test_expected_result(test, c, "${LISTFILTER(list1,&,cd)}", "ab&ef"));
-	TEST(test_expected_result(test, c, "${SHELL(printf 123)},${SHELL(printf 456)}", "123,456"));
-	TEST(test_expected_result(test, c, "${foo},${CDR(answer)},${SHELL(printf 456)}", "123,,456"));
+	TEST(test_expected_result(test, c, "${SHELL(printf '%d' 123)},${SHELL(printf '%d' 456)}", "123,456"));
+	TEST(test_expected_result(test, c, "${foo},${CDR(answer)},${SHELL(printf '%d' 456)}", "123,,456"));
 	TEST(test_expected_result(test, c, "${foo},${this_does_not_exist},${THIS_DOES_NOT_EXIST(either)}", "123,,"));
 #undef TEST