diff --git a/src/app.h b/src/app.h
index 20977a5..32392e6 100644
--- a/src/app.h
+++ b/src/app.h
@@ -94,6 +94,9 @@ struct App{
 		for(auto & l : line.calculate_lines()){
 			sim.lines.push_back(l);
 		}
+		for(auto & u : people_online){
+			u->update_lines = true;
+		}
 	}
 
 	void login(User& user){
diff --git a/src/basics.h b/src/basics.h
index c7baa29..41223d6 100644
--- a/src/basics.h
+++ b/src/basics.h
@@ -28,6 +28,7 @@ struct User {
 	unsigned int index{0};
 	std::string name{"Unknown guest"};
 
+	bool update_lines{true};
 	Size size{0,0};
 	Position position{0,0};
 
diff --git a/src/main.cpp b/src/main.cpp
index f6c5ba3..16f3a09 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -31,7 +31,10 @@ websockets::TestProtocol<User> default_protocol{
 	[](User& user, basic_websocket_info) -> std::string{
 		js::Object ret;
 		ret["balls"] = vector_to_json(app->sim.balls);
-		ret["lines"] = vector_to_json(app->sim.lines);
+		if(user.update_lines){
+			ret["lines"] = vector_to_json(app->sim.lines);
+			user.update_lines = false;
+		}
 		return write_json(ret);
 	},
 	// receive