diff --git a/safedepositbox/build.gradle b/safedepositbox/build.gradle
index 9e2b6e7..336cbfb 100644
--- a/safedepositbox/build.gradle
+++ b/safedepositbox/build.gradle
@@ -9,8 +9,8 @@ android {
     defaultConfig {
         minSdkVersion 21
         targetSdkVersion 29
-        versionCode 2
-        versionName "1.1"
+        versionCode 3
+        versionName "0.3"
         consumerProguardFiles 'consumer-rules.pro'
     }
 
diff --git a/safedepositbox/src/main/java/id/codepresso/safedepositbox/SafeDepositBox.kt b/safedepositbox/src/main/java/id/codepresso/safedepositbox/SafeDepositBox.kt
index 7f299a9..50afb3c 100644
--- a/safedepositbox/src/main/java/id/codepresso/safedepositbox/SafeDepositBox.kt
+++ b/safedepositbox/src/main/java/id/codepresso/safedepositbox/SafeDepositBox.kt
@@ -60,7 +60,7 @@ class SafeDepositBox(private val context: Context, private val prefName: String)
      * @param key SharedPreferences key
      * @param value String value to be stored
      */
-    fun storeString(key: String, value: String) {
+    fun storeString(key: String, value: String?) {
         sharedPrefsEditor.putString(key, value).apply()
     }
 
@@ -340,14 +340,14 @@ class SafeDepositBox(private val context: Context, private val prefName: String)
     /**
      * Get List<T> value from SharedPreferences at 'key'.
      * @param key SharedPreferences key
-     * @return List<T> value at 'key'
+     * @return List<T> value at 'key' or NPE if value not found
      */
     inline fun <reified T : Any> getListObject(key: String): List<T> {
         val objectStrings = getListString(key)
         val objects = mutableListOf<T>()
 
         objectStrings.forEach { objectString ->
-            val value = gson.fromJson(objectString, T::class.java)
+            val value = gson.fromJson(objectString, T::class.java) ?: throw NullPointerException()
             objects.add(value)
         }