diff --git a/packages/client-sync/src/message-processor/detect-thread.js b/packages/client-sync/src/message-processor/detect-thread.js
index 82c4cc6ac..7dafb9215 100644
--- a/packages/client-sync/src/message-processor/detect-thread.js
+++ b/packages/client-sync/src/message-processor/detect-thread.js
@@ -33,6 +33,9 @@ async function findOrBuildByReferences(db, message) {
     });
   }
 
+  if (matchingRef && !matchingRef.thread) {
+    throw new Error(`Reference not properly cleaned up`)
+  }
   return matchingRef ? matchingRef.thread : emptyThread(db, {});
 }