diff --git a/src/vehicle.cpp b/src/vehicle.cpp
index 7e41da1aa9..a385451092 100644
--- a/src/vehicle.cpp
+++ b/src/vehicle.cpp
@@ -237,12 +237,23 @@ bool Vehicle::NeedsServicing() const
 	 * vehicles to go for service is lame. */
 	if (this->vehstatus & (VS_STOPPED | VS_CRASHED)) return false;
 
+	bool service_not_due;
+	/* Service intervals can be measured in different units, which we handle individually. */
+	if (this->ServiceIntervalIsPercent()) {
+		/* Service interval is in percents. */
+		service_not_due = (this->reliability >= this->GetEngine()->reliability * (100 - this->GetServiceInterval()) / 100);
+	} else if (EconTime::UsingWallclockUnits()) {
+		/* Service interval is in minutes. */
+		service_not_due = (this->date_of_last_service + (this->GetServiceInterval() * EconTime::DAYS_IN_ECONOMY_WALLCLOCK_MONTH) >= EconTime::CurDate());
+	} else {
+		/* Service interval is in days. */
+		service_not_due = (this->date_of_last_service + this->GetServiceInterval() >= EconTime::CurDate());
+	}
+
 	/* Are we ready for the next service cycle? */
 	bool needs_service = true;
 	const Company *c = Company::Get(this->owner);
-	if ((this->ServiceIntervalIsPercent() ?
-			(this->reliability >= this->GetEngine()->reliability * (100 - this->service_interval) / 100) :
-			(this->date_of_last_service + this->service_interval >= EconTime::CurDate()))
+	if (service_not_due
 			&& !(this->type == VEH_TRAIN && HasBit(Train::From(this)->flags, VRF_CONSIST_BREAKDOWN) && Train::From(this)->ConsistNeedsRepair())
 			&& !(this->type == VEH_ROAD && RoadVehicle::From(this)->critical_breakdown_count > 0)
 			&& !(this->type == VEH_SHIP && Ship::From(this)->critical_breakdown_count > 0)) {