diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/Protocol.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/Protocol.java
index cc1fc6a..725f1a5 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/Protocol.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/Protocol.java
@@ -105,6 +105,9 @@ public T getHandler() {
      * @return true if the message was sent successfully, false otherwise.
      */
     public boolean sendPacket(@NotNull PacketSender sender, @NotNull M msg) {
+        if (id != 0 && !sender.isEncrypted()) {
+            throw new IllegalStateException("Cannot send packet " + id + " without encryption");
+        }
         try (ByteArrayOutputStream bout = new ByteArrayOutputStream();
              DataOutputStream out = new DataOutputStream(bout)) {
             out.writeByte(id);
@@ -148,6 +151,9 @@ public static void handleProxySide(ServerConnection server, byte[] rawData) {
         try (ByteArrayInputStream bin = new ByteArrayInputStream(data);
              DataInputStream in = new DataInputStream(bin)) {
             byte id = (byte) (in.readByte() & 0xFF);
+            if (id != 0 && !server.isEncrypted()) {
+                throw new RuntimeException("Packet " + id + " must be sent encrypted (server: " + server + ")");
+            }
             Protocol<?, ?> protocol = Protocol.getById(PacketFlow.TO_PROXY, id);
             if (protocol == null) {
                 Logger.getCurrentLogger().warn(
@@ -190,6 +196,9 @@ public static void handleServerSide(@NotNull PacketSender sender, byte[] rawData
         try (ByteArrayInputStream bin = new ByteArrayInputStream(data);
              DataInputStream in = new DataInputStream(bin)) {
             byte id = (byte) (in.readByte() & 0xFF);
+            if (id != 0 && !sender.isEncrypted()) {
+                throw new RuntimeException("Packet " + id + " must be sent encrypted (sender: " + sender + ")");
+            }
             Protocol<?, ?> protocol = Protocol.getById(PacketFlow.TO_SERVER, id);
             if (protocol == null) {
                 Logger.getCurrentLogger().warn("Received unknown protocol id from {}: {}", sender, id);
diff --git a/build.gradle.kts b/build.gradle.kts
index ca3493d..f243433 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -6,7 +6,7 @@ plugins {
 }
 
 group = "net.azisaba.azipluginmessaging"
-version = "2.0.1"
+version = "2.0.2"
 
 repositories {
     mavenCentral()
diff --git a/spigot/src/main/java/net/azisaba/azipluginmessaging/spigot/entity/PlayerImpl.java b/spigot/src/main/java/net/azisaba/azipluginmessaging/spigot/entity/PlayerImpl.java
index cad1a16..fc70d51 100644
--- a/spigot/src/main/java/net/azisaba/azipluginmessaging/spigot/entity/PlayerImpl.java
+++ b/spigot/src/main/java/net/azisaba/azipluginmessaging/spigot/entity/PlayerImpl.java
@@ -17,7 +17,7 @@
 
 public class PlayerImpl implements Player, PacketSender {
     private static final Map<UUID, PlayerImpl> MAP = new ConcurrentHashMap<>();
-    private final org.bukkit.entity.Player handle;
+    private org.bukkit.entity.Player handle;
     private KeyPair keyPair;
     private PublicKey remotePublicKey;
     private boolean encrypted = false;
@@ -33,7 +33,9 @@ private PlayerImpl(@Nullable org.bukkit.entity.Player handle) {
 
     @NotNull
     public static PlayerImpl of(@NotNull org.bukkit.entity.Player player) {
-        return MAP.computeIfAbsent(player.getUniqueId(), u -> new PlayerImpl(player));
+        PlayerImpl p = MAP.computeIfAbsent(player.getUniqueId(), u -> new PlayerImpl(player));
+        p.handle = player;
+        return p;
     }
 
     @NotNull