diff --git a/contribs/drt-extensions/src/main/java/org/matsim/contrib/drt/extension/preplanned/optimizer/PreplannedDrtOptimizer.java b/contribs/drt-extensions/src/main/java/org/matsim/contrib/drt/extension/preplanned/optimizer/PreplannedDrtOptimizer.java
index fd0f6672826..5e47c385106 100644
--- a/contribs/drt-extensions/src/main/java/org/matsim/contrib/drt/extension/preplanned/optimizer/PreplannedDrtOptimizer.java
+++ b/contribs/drt-extensions/src/main/java/org/matsim/contrib/drt/extension/preplanned/optimizer/PreplannedDrtOptimizer.java
@@ -77,7 +77,7 @@ public PreplannedDrtOptimizer(DrtConfigGroup drtCfg, PreplannedSchedules preplan
 			TravelTime travelTime, TravelDisutility travelDisutility, MobsimTimer timer, DrtTaskFactory taskFactory,
 			EventsManager eventsManager, Fleet fleet, ScheduleTimingUpdater scheduleTimingUpdater) {
 		Preconditions.checkArgument(
-				fleet.getVehicles().keySet().equals(preplannedSchedules.vehicleToPreplannedStops.keySet()),
+				fleet.getVehicles().keySet().containsAll(preplannedSchedules.vehicleToPreplannedStops.keySet()),
 				"Some schedules are preplanned for vehicles outside the fleet");
 
 		this.mode = drtCfg.getMode();