diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java b/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java
index 73010709a..357cde6fd 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java
@@ -551,6 +551,7 @@ public class WhisperServerService extends Application<WhisperServerConfiguration
     WebSocketEnvironment<Account> webSocketEnvironment = new WebSocketEnvironment<>(environment, config.getWebSocketConfiguration(), 90000);
     webSocketEnvironment.setAuthenticator(new WebSocketAccountAuthenticator(accountAuthenticator));
     webSocketEnvironment.setConnectListener(new AuthenticatedConnectListener(receiptSender, messagesManager, messageSender, apnFallbackManager, clientPresenceManager, retrySchedulingExecutor));
+    webSocketEnvironment.jersey().register(MultiRecipientMessageProvider.class);
     webSocketEnvironment.jersey().register(new MetricsApplicationEventListener(TrafficSource.WEBSOCKET));
     webSocketEnvironment.jersey().register(new KeepAliveController(clientPresenceManager));
     webSocketEnvironment.jersey().register(messageController);