diff --git a/src/state.hpp b/src/state.hpp
index 4aafa162..5525cb3d 100644
--- a/src/state.hpp
+++ b/src/state.hpp
@@ -9,7 +9,8 @@
 
 struct PassthroughDetails
 {
-  std::atomic<u64>
+  std::atomic<u64> ref_count;
+  int backing_id;
 };
 
 class State