diff --git a/src/chain.h b/src/chain.h
index 2abb23c5a..e47b38568 100644
--- a/src/chain.h
+++ b/src/chain.h
@@ -324,6 +324,11 @@ public:
             READWRITE(VARINT(nDataPos));
         if (nStatus & BLOCK_HAVE_UNDO)
             READWRITE(VARINT(nUndoPos));
+        uint8_t tag = 0;
+        READWRITE(tag);
+        if (ser_action.ForRead() && tag != 0) {
+            assert(!"For the first time running zcashd after upgrading to v1.0.0-rc1, please use the -reindex option.");
+        }
         READWRITE(hashAnchor);
 
         // block header