diff --git a/lib/message.cc b/lib/message.cc
index e6a5a5af..90a01eb8 100644
--- a/lib/message.cc
+++ b/lib/message.cc
@@ -1032,6 +1032,8 @@ _notmuch_message_gen_terms (notmuch_message_t *message,
 	/* Create a gap between this an the next terms so they don't
 	 * appear to be a phrase. */
 	message->termpos = term_gen->get_termpos () + 100;
+
+	_notmuch_message_invalidate_metadata (message, prefix_name);
     }
 
     term_gen->set_termpos (message->termpos);