diff --git a/src/citymania/cm_highlight.cpp b/src/citymania/cm_highlight.cpp
index d1f79ab499..fda507d26c 100644
--- a/src/citymania/cm_highlight.cpp
+++ b/src/citymania/cm_highlight.cpp
@@ -1214,9 +1214,11 @@ HighLightStyle UpdateTileSelection(HighLightStyle new_drawstyle) {
     // } else if (((_thd.place_mode & HT_DRAG_MASK) == HT_RECT || ((_thd.place_mode & HT_DRAG_MASK) == HT_SPECIAL && (_thd.next_drawstyle & HT_DRAG_MASK) == HT_RECT)) && _thd.new_outersize.x > 0 && !_thd.make_square_red) {  // station
     } else if (_thd.select_proc == CM_DDSP_BUILD_AIRPORT) {
         auto tile = TileXY(_thd.new_pos.x / TILE_SIZE, _thd.new_pos.y / TILE_SIZE);
-        const AirportSpec *as = AirportClass::Get(_selected_airport_class)->GetSpec(_selected_airport_index);
-        _thd.cm_new = ObjectHighlight::make_airport(tile, as->GetIndex(), _selected_airport_layout);
-        new_drawstyle = HT_RECT;
+        if (_selected_airport_index != -1) {
+            const AirportSpec *as = AirportClass::Get(_selected_airport_class)->GetSpec(_selected_airport_index);
+            _thd.cm_new = ObjectHighlight::make_airport(tile, as->GetIndex(), _selected_airport_layout);
+            new_drawstyle = HT_RECT;
+        }
     } else if (_thd.select_proc == DDSP_BUILD_STATION || _thd.select_proc == DDSP_BUILD_BUSSTOP
                || _thd.select_proc == DDSP_BUILD_TRUCKSTOP) {  // station
         if (_thd.size.x >= (int)TILE_SIZE && _thd.size.y >= (int)TILE_SIZE) {