diff --git a/src/newgrf_airport.cpp b/src/newgrf_airport.cpp
--- a/src/newgrf_airport.cpp
+++ b/src/newgrf_airport.cpp
@@ -26,7 +26,18 @@ struct AirportScopeResolver : public Sco
 	byte layout;        ///< Layout of the airport to build.
 	TileIndex tile;     ///< Tile for the callback, only valid for airporttile callbacks.
 
-	AirportScopeResolver(ResolverObject &ro, TileIndex tile, Station *st, byte airport_id, byte layout);
+	/**
+	 * Constructor of the scope resolver for an airport.
+	 * @param ro Surrounding resolver.
+	 * @param tile %Tile for the callback, only valid for airporttile callbacks.
+	 * @param st %Station of the airport for which the callback is run, or \c NULL for build gui.
+	 * @param airport_id Type of airport for which the callback is run.
+	 * @param layout Layout of the airport to build.
+	 */
+	AirportScopeResolver(ResolverObject &ro, TileIndex tile, Station *st, byte airport_id, byte layout)
+			: ScopeResolver(ro), st(st), airport_id(airport_id), layout(layout), tile(tile)
+	{
+	}
 
 	/* virtual */ uint32 GetRandomBits() const;
 	/* virtual */ uint32 GetVariable(byte variable, uint32 parameter, bool *available) const;
@@ -242,22 +253,6 @@ AirportResolverObject::AirportResolverOb
 	this->root_spritegroup = AirportSpec::Get(airport_id)->grf_prop.spritegroup[0];
 }
 
-/**
- * Constructor of the scope resolver for an airport.
- * @param ro Surrounding resolver.
- * @param tile %Tile for the callback, only valid for airporttile callbacks.
- * @param st %Station of the airport for which the callback is run, or \c NULL for build gui.
- * @param airport_id Type of airport for which the callback is run.
- * @param layout Layout of the airport to build.
- */
-AirportScopeResolver::AirportScopeResolver(ResolverObject &ro, TileIndex tile, Station *st, byte airport_id, byte layout) : ScopeResolver(ro)
-{
-	this->st = st;
-	this->airport_id = airport_id;
-	this->layout = layout;
-	this->tile = tile;
-}
-
 SpriteID GetCustomAirportSprite(const AirportSpec *as, byte layout)
 {
 	AirportResolverObject object(INVALID_TILE, NULL, as->GetIndex(), layout);