diff --git a/src/newgrf_airport.cpp b/src/newgrf_airport.cpp
--- a/src/newgrf_airport.cpp
+++ b/src/newgrf_airport.cpp
@@ -212,7 +212,7 @@ void AirportOverrideManager::SetEntitySp
 		case 0x7C: return (this->st->airport.psa != nullptr) ? this->st->airport.psa->GetValue(parameter) : 0;
 
 		case 0xF0: return this->st->facilities;
-		case 0xFA: return Clamp(this->st->build_date - DAYS_TILL_ORIGINAL_BASE_YEAR, 0, 65535);
+		case 0xFA: return ClampTo<uint16_t>(this->st->build_date - DAYS_TILL_ORIGINAL_BASE_YEAR);
 	}
 
 	return this->st->GetNewGRFVariable(this->ro, variable, parameter, available);