diff --git a/exp_scenario/module/control/vlayer.lua b/exp_scenario/module/control/vlayer.lua
index 786c2e2a..e3308163 100644
--- a/exp_scenario/module/control/vlayer.lua
+++ b/exp_scenario/module/control/vlayer.lua
@@ -293,7 +293,7 @@ end
 --- @return number
 local function get_production_multiplier(s_index)
     ---@diagnostic disable-next-line: undefined-field
-    local surface = assert(config.global_surface and game.surface[1] or game.surfaces[s_index])
+    local surface = assert(config.global_surface and game.surface[1] or game.surfaces[s_index]) --[[@as LuaSurface]]
     local multiplier = surface.solar_power_multiplier
     if surface.always_day then
         return multiplier
@@ -325,7 +325,8 @@ end
 --- @param s_index number Surface index
 --- @return number
 local function get_sustained_multiplier(s_index)
-    local surface = assert(config.global_surface and game.surface[1] or game.surfaces[s_index])
+    ---@diagnostic disable-next-line: undefined-field
+    local surface = assert(config.global_surface and game.surface[1] or game.surfaces[s_index]) --[[@as LuaSurface]]
     local multiplier = surface.solar_power_multiplier
     if surface.always_day then
         return multiplier