diff --git a/pandalib-ws-client/src/main/java/fr/pandacube/lib/ws/client/AbstractClientWS.java b/pandalib-ws-client/src/main/java/fr/pandacube/lib/ws/client/AbstractClientWS.java
index c8893de..c1e7172 100644
--- a/pandalib-ws-client/src/main/java/fr/pandacube/lib/ws/client/AbstractClientWS.java
+++ b/pandalib-ws-client/src/main/java/fr/pandacube/lib/ws/client/AbstractClientWS.java
@@ -110,7 +110,7 @@ public abstract class AbstractClientWS implements AbstractWS {
     public final void sendClose(int code, String reason) throws IOException {
         synchronized (socket) {
             autoReconnect = false; // if we ask for closing connection, dont reconnect automatically
-            socket.get().sendClose(code, reason);
+            socket.get().sendClose(code, reason).join();
         }
     }
 
diff --git a/pandalib-ws/src/main/java/fr/pandacube/lib/ws/payloads/ErrorPayload.java b/pandalib-ws/src/main/java/fr/pandacube/lib/ws/payloads/ErrorPayload.java
index 6c69902..37ca2f6 100644
--- a/pandalib-ws/src/main/java/fr/pandacube/lib/ws/payloads/ErrorPayload.java
+++ b/pandalib-ws/src/main/java/fr/pandacube/lib/ws/payloads/ErrorPayload.java
@@ -1,5 +1,7 @@
 package fr.pandacube.lib.ws.payloads;
 
+import fr.pandacube.lib.util.ThrowableUtil;
+
 /**
  * Error message payload.
  */
@@ -11,7 +13,7 @@ public class ErrorPayload extends Payload {
     /**
      * The error Throwable, may be null.
      */
-    public Throwable throwable;
+    public String exception;
 
     /**
      * Initialize an error payload with a message but not throwable.
@@ -28,7 +30,7 @@ public class ErrorPayload extends Payload {
      */
     public ErrorPayload(String message, Throwable throwable) {
         this.message = message;
-        this.throwable = throwable;
+        this.exception = ThrowableUtil.stacktraceToString(throwable);
     }
 
     @SuppressWarnings("unused")