diff --git a/.classpath b/.classpath
index e716709..43b52b8 100644
--- a/.classpath
+++ b/.classpath
@@ -8,9 +8,9 @@
 	</classpathentry>
 	<classpathentry kind="src" output="target/test-classes" path="src/test/java">
 		<attributes>
+			<attribute name="test" value="true"/>
 			<attribute name="optional" value="true"/>
 			<attribute name="maven.pomderived" value="true"/>
-			<attribute name="test" value="true"/>
 		</attributes>
 	</classpathentry>
 	<classpathentry kind="con" path="org.eclipse.m2e.MAVEN2_CLASSPATH_CONTAINER">
@@ -21,9 +21,9 @@
 	</classpathentry>
 	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-11">
 		<attributes>
+			<attribute name="module" value="true"/>
 			<attribute name="maven.pomderived" value="true"/>
 		</attributes>
 	</classpathentry>
-	<classpathentry kind="con" path="org.eclipse.jdt.junit.JUNIT_CONTAINER/5"/>
 	<classpathentry kind="output" path="target/classes"/>
 </classpath>
diff --git a/pom.xml b/pom.xml
index 98d18f7..aa2ee32 100644
--- a/pom.xml
+++ b/pom.xml
@@ -16,6 +16,13 @@
 		<maven.compiler.target>11</maven.compiler.target>
 	</properties>
 
+	<dependencies>
+		<dependency>
+			<groupId>org.junit.jupiter</groupId>
+			<artifactId>junit-jupiter-engine</artifactId>
+			<version>5.5.2</version>
+		</dependency>
+	</dependencies>
 	<build>
 		<finalName>envoy-common</finalName>
 		<resources>
@@ -23,7 +30,7 @@
 				<directory>src/main/resources</directory>
 			</resource>
 		</resources>
- 		<testSourceDirectory>src/test/java</testSourceDirectory>
+		<testSourceDirectory>src/test/java</testSourceDirectory>
 		<pluginManagement>
 			<plugins>
 				<plugin>
diff --git a/src/main/java/envoy/data/Contact.java b/src/main/java/envoy/data/Contact.java
index b3b2d03..4de77a0 100644
--- a/src/main/java/envoy/data/Contact.java
+++ b/src/main/java/envoy/data/Contact.java
@@ -28,7 +28,7 @@ public abstract class Contact implements Serializable {
 	 *
 	 * @param id       the ID of this contact
 	 * @param name     the name of this contact
-	 * @param contacts the {@link Contacts} of this {@link Contact}
+	 * @param contacts the contacts of this {@link Contact}
 	 * @since Envoy Common v0.1-beta
 	 */
 	public Contact(long id, String name, Set<? extends Contact> contacts) {
diff --git a/src/main/java/envoy/data/User.java b/src/main/java/envoy/data/User.java
index ca64d0d..01b2439 100644
--- a/src/main/java/envoy/data/User.java
+++ b/src/main/java/envoy/data/User.java
@@ -2,7 +2,6 @@ package envoy.data;
 
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
-import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.Set;
 
@@ -126,7 +125,7 @@ public final class User extends Contact {
 		if (serializeContacts) {
 			getContacts().stream().filter(User.class::isInstance).map(User.class::cast).forEach(user -> user.serializeContacts = false);
 			outputStream.writeObject(getContacts());
-		} else outputStream.writeObject(new ArrayList<>());
+		} else outputStream.writeObject(new HashSet<>());
 	}
 
 	/**