diff --git a/test/sexpression/SExpressionTester.java b/test/sexpression/SExpressionTester.java
index 6f5a786..4189204 100644
--- a/test/sexpression/SExpressionTester.java
+++ b/test/sexpression/SExpressionTester.java
@@ -166,6 +166,7 @@ public class SExpressionTester {
 
     @Test
     public void testLispNumberConstants() {
+        assertEquals(LispNumber.ZERO.getValue(), new BigInteger("0"));
         assertEquals(LispNumber.ONE.getValue(), new BigInteger("1"));
     }