diff --git a/src/main/java/com/insightfullogic/java8/answers/chapter3/StringExercises.java b/src/main/java/com/insightfullogic/java8/answers/chapter3/StringExercises.java
index 336b9b9f..80d5a340 100644
--- a/src/main/java/com/insightfullogic/java8/answers/chapter3/StringExercises.java
+++ b/src/main/java/com/insightfullogic/java8/answers/chapter3/StringExercises.java
@@ -2,12 +2,14 @@
 
 import java.util.Comparator;
 import java.util.List;
+import java.util.Objects;
 import java.util.Optional;
 
 public class StringExercises {
 
     // Question 6
     public static int countLowercaseLetters(String string) {
+        if (Objects.isNull(string)) return 0;
         return (int) string.chars()
                            .filter(Character::isLowerCase)
                            .count();