diff --git a/src/test/java/org/apache/commons/text/similarity/SimilarityCharacterInputTest.java b/src/test/java/org/apache/commons/text/similarity/SimilarityCharacterInputTest.java
index a8d2ae8400..218fce1916 100644
--- a/src/test/java/org/apache/commons/text/similarity/SimilarityCharacterInputTest.java
+++ b/src/test/java/org/apache/commons/text/similarity/SimilarityCharacterInputTest.java
@@ -42,6 +42,8 @@ void testEquals(final Class<?> cls) {
         assertNotEquals(similarityInput1, similarityInput4);
         assertNotEquals(similarityInput2, similarityInput4);
         assertNotEquals(similarityInput3, similarityInput4);
+        assertNotEquals(similarityInput1, null);
+        assertNotEquals(similarityInput1, new Object());
     }
 
     @ParameterizedTest