diff --git a/networktransport.cpp b/networktransport.cpp
index d1f8190..7c9adaf 100644
--- a/networktransport.cpp
+++ b/networktransport.cpp
@@ -74,7 +74,8 @@ void Transport<MyState, RemoteState>::send_to_receiver( void )
   if ( diff.empty() ) {
     /* send empty ack */
     if ( (!connection.pending_timestamp())
-	 && (timestamp() - sent_states.back().timestamp < int64_t( ACK_INTERVAL )) ) {
+	 && (timestamp() - sent_states.back().timestamp < int64_t( ACK_INTERVAL ))
+	 && (sent_states.back().num > 0) ) {
       return;
     }
 
diff --git a/terminalframebuffer.hpp b/terminalframebuffer.hpp
index 708630a..59d22e1 100644
--- a/terminalframebuffer.hpp
+++ b/terminalframebuffer.hpp
@@ -157,7 +157,7 @@ namespace Terminal {
       /* XXX other fields not necessary to compare -- for now */
       return ( width == x.width ) && ( height == x.height ) && ( cursor_col == x.cursor_col )
 	&& ( cursor_row == x.cursor_row ) && ( cursor_visible == x.cursor_visible ) &&
-	( reverse_video == x.reverse_video ) && ( renditions == x.renditions );
+	( reverse_video == x.reverse_video ) && ( renditions == x.renditions ) && ( tabs == x.tabs );
     }
   };