diff --git a/matsim/src/main/java/org/matsim/core/config/groups/QSimConfigGroup.java b/matsim/src/main/java/org/matsim/core/config/groups/QSimConfigGroup.java
index 14c9504e785..f8d59f01e01 100644
--- a/matsim/src/main/java/org/matsim/core/config/groups/QSimConfigGroup.java
+++ b/matsim/src/main/java/org/matsim/core/config/groups/QSimConfigGroup.java
@@ -32,6 +32,7 @@
 import jakarta.validation.constraints.Positive;
 import jakarta.validation.constraints.PositiveOrZero;
 import java.util.*;
+import java.util.stream.Collectors;
 
 /**
  * @author nagel
@@ -240,25 +241,26 @@ public final Map<String, String> getComments() {
 	public enum NodeTransition {
 		emptyBufferAfterBufferRandomDistribution_dontBlockNode,
 		emptyBufferAfterBufferRandomDistribution_nodeBlockedWhenSingleOutlinkFull,
-		moveVehByVehRandomDistribution_dontBlockNode, 
-		moveVehByVehRandomDistribution_nodeBlockedWhenSingleOutlinkFull, 
+		moveVehByVehRandomDistribution_dontBlockNode,
+		moveVehByVehRandomDistribution_nodeBlockedWhenSingleOutlinkFull,
 		moveVehByVehDeterministicPriorities_nodeBlockedWhenSingleOutlinkFull
-		/* note: moveVehByVehDeterministicPriorities is not implemented for the case when the node is not blocked 
+		/* note: moveVehByVehDeterministicPriorities is not implemented for the case when the node is not blocked
 		 * as soon as a single outlink is full
 		 * theresa, jun'20
 		 */
 	}
 	private NodeTransition nodeTransitionLogic = NodeTransition.emptyBufferAfterBufferRandomDistribution_dontBlockNode;
-	
+
 	// ---
-	
+
 	public QSimConfigGroup() {
 		super(GROUP_NAME);
 	}
 
 	@StringSetter(MAIN_MODE)
 	private void setMainModes(String value) {
-		setMainModes(Arrays.asList(value.split(",")));
+		Set<String> modes = Arrays.stream(value.split(",")).map(String::trim).collect(Collectors.toSet());
+		setMainModes(modes);
 	}
 
 	@StringSetter(SNAPSHOT_PERIOD)
@@ -600,7 +602,8 @@ private String getSeepModesAsString() {
 
 	@StringSetter(SEEP_MODE)
 	private void setSeepModes(String value) {
-		setSeepModes(Arrays.asList(value.split(",")));
+		Set<String> modes = Arrays.stream(value.split(",")).map(String::trim).collect(Collectors.toSet());
+		setSeepModes(modes);
 	}
 
 	public Collection<String> getSeepModes() {
@@ -641,16 +644,16 @@ public boolean setUsingTravelTimeCheckInTeleportation( boolean val ) {
 		// yyyyyy this should better become a threshold number!  kai, aug'16
 		return this.usingTravelTimeCheckInTeleportation = val ;
 	}
-	
+
 	static final String PCU_THRESHOLD_FOR_FLOW_CAPACITY_EASING = //
 			"Flow capacity easing is activated for vehicles of size equal or smaller than the specified threshold. "
 			+ "Introduced to minimise the chances of buses being severely delayed in downsampled scenarios";
-	
-	
+
+
 	public double getPcuThresholdForFlowCapacityEasing() {
 		return pcuThresholdForFlowCapacityEasing;
 	}
-	
+
 	/**
 	 * @param pcuThresholdForFlowCapacityEasing -- {@value #PCU_THRESHOLD_FOR_FLOW_CAPACITY_EASING}
 	 */
@@ -685,5 +688,5 @@ public void setInflowCapacitySetting(InflowCapacitySetting inflowCapacitySetting
 //		// yyyy do we really need this switch?  Quite in general, please try to avoid boolean switches.  kai, may'18
 //		this.creatingVehiclesForAllNetworkModes = creatingVehiclesForAllNetworkModes;
 //	}
-	
+
 }