diff --git a/src/sync.ts b/src/sync.ts
index c119240..e38e502 100644
--- a/src/sync.ts
+++ b/src/sync.ts
@@ -161,8 +161,8 @@ const ensembleMixedStates = async (
         r = {
           key: key,
           exist_remote: true,
-          mtime_remote: backwardMapping.localMtime,
-          size_remote: backwardMapping.localSize,
+          mtime_remote: backwardMapping.localMtime || entry.lastModified,
+          size_remote: backwardMapping.localSize || entry.size,
           remote_encrypted_key: remoteEncryptedKey,
         };
       } else {
@@ -388,6 +388,10 @@ const getOperation = (
     r.decision_branch = 11;
   }
 
+  if (r.decision === "unknown") {
+    throw Error(`unknown decision for ${r}`);
+  }
+
   return r;
 };