diff --git a/src/lang/persian.txt b/src/lang/persian.txt
--- a/src/lang/persian.txt
+++ b/src/lang/persian.txt
@@ -2107,6 +2107,8 @@ STR_LINKGRAPH_LEGEND_UNUSED                                     :{TINY_FONT}{BLACK}بلااستفاده
 STR_LINKGRAPH_LEGEND_SATURATED                                  :{TINY_FONT}{BLACK}اشباع شده
 STR_LINKGRAPH_LEGEND_OVERLOADED                                 :{TINY_FONT}{BLACK}بیش از ظرفیت
 
+# Linkgraph tooltip
+
 # Base for station construction window(s)
 STR_STATION_BUILD_COVERAGE_AREA_TITLE                           :{BLACK}نور ناحیه ی اطراف ایستگاه
 STR_STATION_BUILD_COVERAGE_OFF                                  :{BLACK}خاموش