diff --git a/src/main/java/kyu7/Maskify.java b/src/main/java/kyu7/Maskify.java
index 42ddda5..34bccb8 100644
--- a/src/main/java/kyu7/Maskify.java
+++ b/src/main/java/kyu7/Maskify.java
@@ -7,7 +7,7 @@ public class Maskify {
     //7 https://www.codewars.com/kata/5412509bd436bd33920011bc/train/java
 
     public static String maskify(String str) {
-        if (str.length() < 5) return str;
+        if (str == null || str.length() < 5) return str;
         return "#".repeat(str.length() - 4) + str.substring(str.length() - 4);
     }
 
diff --git a/src/test/java/kyu7/MaskifyTest.java b/src/test/java/kyu7/MaskifyTest.java
index 803a117..aa874aa 100644
--- a/src/test/java/kyu7/MaskifyTest.java
+++ b/src/test/java/kyu7/MaskifyTest.java
@@ -17,6 +17,11 @@
 import static kyu7.Maskify.*;
 @Tag("smoke")
 public class MaskifyTest {
+    @Test
+    void nullInputShouldRemainNull() {
+        assertNull(maskify(null));
+    }
+
     @Test
     void smokeTestsShouldExecuteApi() {
         quality.SmokeMethodTestHarness.verify(kyu7.Maskify.class);