diff --git a/src/newgrf_airport.cpp b/src/newgrf_airport.cpp
--- a/src/newgrf_airport.cpp
+++ b/src/newgrf_airport.cpp
@@ -127,7 +127,7 @@ void AirportOverrideManager::SetEntitySp
 	}
 }
 
-uint32 AirportGetVariable(const ResolverObject *object, byte variable, byte parameter, bool *available)
+uint32 AirportGetVariable(const ResolverObject *object, byte variable, uint32 parameter, bool *available)
 {
 	const Station *st = object->u.airport.st;
 	byte layout       = object->u.airport.layout;