diff --git a/libuavcan/include/uavcan/internal/transport/transfer_buffer.hpp b/libuavcan/include/uavcan/internal/transport/transfer_buffer.hpp
index 3fb166bf6a..0a559ff6c0 100644
--- a/libuavcan/include/uavcan/internal/transport/transfer_buffer.hpp
+++ b/libuavcan/include/uavcan/internal/transport/transfer_buffer.hpp
@@ -454,6 +454,8 @@ public:
     {
         (void)key;
     }
+
+    bool isEmpty() const { return true; }
 };
 
 }