diff --git a/catkit_core/MessageBroker.h b/catkit_core/MessageBroker.h
index 5b3a8e11..25fdf79c 100644
--- a/catkit_core/MessageBroker.h
+++ b/catkit_core/MessageBroker.h
@@ -101,6 +101,8 @@ struct MessageBrokerHeader
 	CudaIpcHandle cuda_ipc_handles[MAX_NUM_GPUS];
 };
 
+class MessageBroker;
+
 class Message
 {
 	friend class MessageBroker;