diff --git a/src/main/java/Credential.java b/src/main/java/Credential.java
index 506fdb7..913780c 100644
--- a/src/main/java/Credential.java
+++ b/src/main/java/Credential.java
@@ -1,4 +1,6 @@
-public class Credential {
+import java.io.Serializable;
+
+public class Credential implements Serializable {
 
     private String name, password;
     private int id;
diff --git a/src/main/java/CredentialList.java b/src/main/java/CredentialList.java
new file mode 100644
index 0000000..f81053f
--- /dev/null
+++ b/src/main/java/CredentialList.java
@@ -0,0 +1,4 @@
+import java.io.Serializable;
+import java.util.ArrayList;
+
+public class CredentialList extends ArrayList<Credential> implements Serializable{}
diff --git a/src/main/java/CredentialRepository.java b/src/main/java/CredentialRepository.java
index aff2d70..242acdb 100644
--- a/src/main/java/CredentialRepository.java
+++ b/src/main/java/CredentialRepository.java
@@ -1,8 +1,5 @@
-import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
-import java.io.IOException;
 import java.io.ObjectOutputStream;
-import java.util.ArrayList;
 
 /**
  * Credential Repository for handling user credentials
@@ -12,7 +9,7 @@ import java.util.ArrayList;
 public class CredentialRepository implements CredentialRepositoryInterface{
 
     private int idCounter = 0;
-    private ArrayList<Credential> credentials;
+    private CredentialList credentials;
 
     /**
      * Konstruktor
@@ -21,7 +18,7 @@ public class CredentialRepository implements CredentialRepositoryInterface{
      */
     public CredentialRepository()
     {
-        this.credentials = new ArrayList<Credential>();
+        this.credentials = new CredentialList();
     }
 
 
@@ -147,6 +144,7 @@ public class CredentialRepository implements CredentialRepositoryInterface{
             out.writeObject(this.credentials);
         } catch (Exception fail) {
             System.err.println("Serialization failed!");
+            fail.printStackTrace();
         }
     }