diff --git a/exercises/concept/rpn-calculator/tests/rpn-calculator.rs b/exercises/concept/rpn-calculator/tests/rpn-calculator.rs
index 5349bd091..eba9c5f96 100644
--- a/exercises/concept/rpn-calculator/tests/rpn-calculator.rs
+++ b/exercises/concept/rpn-calculator/tests/rpn-calculator.rs
@@ -73,3 +73,17 @@ fn test_too_many_operands_returns_none() {
     let input = calculator_input("2 2");
     assert_eq!(evaluate(&input), None);
 }
+
+#[test]
+#[ignore]
+fn test_zero_operands_returns_none() {
+    let input = calculator_input("+");
+    assert_eq!(evaluate(&input), None);
+}
+
+#[test]
+#[ignore]
+fn test_intermediate_error_returns_none() {
+    let input = calculator_input("+ 2 2 *");
+    assert_eq!(evaluate(&input), None);
+}