diff --git a/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/AbstractInsertionCalculator.java b/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/AbstractInsertionCalculator.java
index fc82d6ad..6f3d54a4 100644
--- a/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/AbstractInsertionCalculator.java
+++ b/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/AbstractInsertionCalculator.java
@@ -21,7 +21,6 @@ package com.graphhopper.jsprit.core.algorithm.recreate;
 import com.graphhopper.jsprit.core.problem.constraint.ConstraintManager;
 import com.graphhopper.jsprit.core.problem.constraint.HardActivityConstraint;
 import com.graphhopper.jsprit.core.problem.constraint.HardActivityConstraint.ConstraintsStatus;
-import com.graphhopper.jsprit.core.problem.constraint.HardConstraint;
 import com.graphhopper.jsprit.core.problem.constraint.HardRouteConstraint;
 import com.graphhopper.jsprit.core.problem.misc.JobInsertionContext;
 import com.graphhopper.jsprit.core.problem.solution.route.activity.TourActivity;
@@ -46,17 +45,17 @@ abstract class AbstractInsertionCalculator implements JobInsertionCostsCalculato
         return null;
     }
 
-    ConstraintsStatus fulfilled(JobInsertionContext iFacts, TourActivity prevAct, TourActivity newAct, TourActivity nextAct, double prevActDepTime, Collection<HardConstraint> failedActivityConstraints, ConstraintManager constraintManager) {
+    ConstraintsStatus fulfilled(JobInsertionContext iFacts, TourActivity prevAct, TourActivity newAct, TourActivity nextAct, double prevActDepTime, Collection<String> failedActivityConstraints, ConstraintManager constraintManager) {
         ConstraintsStatus notFulfilled = null;
-        List<HardConstraint> failed = new ArrayList<>();
+        List<String> failed = new ArrayList<>();
         for (HardActivityConstraint c : constraintManager.getCriticalHardActivityConstraints()) {
             ConstraintsStatus status = c.fulfilled(iFacts, prevAct, newAct, nextAct, prevActDepTime);
             if (status.equals(ConstraintsStatus.NOT_FULFILLED_BREAK)) {
-                failedActivityConstraints.add(c);
+                failedActivityConstraints.add(c.getClass().getSimpleName());
                 return status;
             } else {
                 if (status.equals(ConstraintsStatus.NOT_FULFILLED)) {
-                    failed.add(c);
+                    failed.add(c.getClass().getSimpleName());
                     notFulfilled = status;
                 }
             }
@@ -69,11 +68,11 @@ abstract class AbstractInsertionCalculator implements JobInsertionCostsCalculato
         for (HardActivityConstraint c : constraintManager.getHighPrioHardActivityConstraints()) {
             ConstraintsStatus status = c.fulfilled(iFacts, prevAct, newAct, nextAct, prevActDepTime);
             if (status.equals(ConstraintsStatus.NOT_FULFILLED_BREAK)) {
-                failedActivityConstraints.add(c);
+                failedActivityConstraints.add(c.getClass().getSimpleName());
                 return status;
             } else {
                 if (status.equals(ConstraintsStatus.NOT_FULFILLED)) {
-                    failed.add(c);
+                    failed.add(c.getClass().getSimpleName());
                     notFulfilled = status;
                 }
             }
@@ -86,7 +85,7 @@ abstract class AbstractInsertionCalculator implements JobInsertionCostsCalculato
         for (HardActivityConstraint constraint : constraintManager.getLowPrioHardActivityConstraints()) {
             ConstraintsStatus status = constraint.fulfilled(iFacts, prevAct, newAct, nextAct, prevActDepTime);
             if (status.equals(ConstraintsStatus.NOT_FULFILLED_BREAK) || status.equals(ConstraintsStatus.NOT_FULFILLED)) {
-                failedActivityConstraints.add(constraint);
+                failedActivityConstraints.add(constraint.getClass().getSimpleName());
                 return status;
             }
         }
diff --git a/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/ServiceInsertionCalculator.java b/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/ServiceInsertionCalculator.java
index 1ed5a68b..6007decb 100644
--- a/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/ServiceInsertionCalculator.java
+++ b/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/ServiceInsertionCalculator.java
@@ -20,7 +20,6 @@ package com.graphhopper.jsprit.core.algorithm.recreate;
 import com.graphhopper.jsprit.core.problem.JobActivityFactory;
 import com.graphhopper.jsprit.core.problem.constraint.ConstraintManager;
 import com.graphhopper.jsprit.core.problem.constraint.HardActivityConstraint.ConstraintsStatus;
-import com.graphhopper.jsprit.core.problem.constraint.HardConstraint;
 import com.graphhopper.jsprit.core.problem.constraint.SoftActivityConstraint;
 import com.graphhopper.jsprit.core.problem.constraint.SoftRouteConstraint;
 import com.graphhopper.jsprit.core.problem.cost.VehicleRoutingActivityCosts;
@@ -109,7 +108,7 @@ final class ServiceInsertionCalculator extends AbstractInsertionCalculator {
         InsertionData noInsertion = checkRouteContraints(insertionContext, constraintManager);
         if (noInsertion != null) return noInsertion;
 
-        Collection<HardConstraint> failedActivityConstraints = new ArrayList<>();
+        Collection<String> failedActivityConstraints = new ArrayList<>();
 
         /*
         check soft constraints at route level
@@ -168,9 +167,7 @@ final class ServiceInsertionCalculator extends AbstractInsertionCalculator {
         }
         if(insertionIndex == InsertionData.NO_INDEX) {
             InsertionData emptyInsertionData = new InsertionData.NoInsertionFound();
-            for (HardConstraint c : failedActivityConstraints) {
-                emptyInsertionData.addFailedConstrainName(c.getClass().getSimpleName());
-            }
+            emptyInsertionData.getFailedConstraintNames().addAll(failedActivityConstraints);
             return emptyInsertionData;
         }
         InsertionData insertionData = new InsertionData(bestCost, InsertionData.NO_INDEX, insertionIndex, newVehicle, newDriver);
diff --git a/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/ShipmentInsertionCalculator.java b/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/ShipmentInsertionCalculator.java
index d7b3eecd..9eb5967c 100644
--- a/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/ShipmentInsertionCalculator.java
+++ b/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/ShipmentInsertionCalculator.java
@@ -20,7 +20,6 @@ package com.graphhopper.jsprit.core.algorithm.recreate;
 import com.graphhopper.jsprit.core.problem.JobActivityFactory;
 import com.graphhopper.jsprit.core.problem.constraint.ConstraintManager;
 import com.graphhopper.jsprit.core.problem.constraint.HardActivityConstraint.ConstraintsStatus;
-import com.graphhopper.jsprit.core.problem.constraint.HardConstraint;
 import com.graphhopper.jsprit.core.problem.constraint.SoftActivityConstraint;
 import com.graphhopper.jsprit.core.problem.constraint.SoftRouteConstraint;
 import com.graphhopper.jsprit.core.problem.cost.VehicleRoutingActivityCosts;
@@ -129,7 +128,7 @@ final class ShipmentInsertionCalculator extends AbstractInsertionCalculator {
         //pickupShipmentLoop
         List<TourActivity> activities = currentRoute.getTourActivities().getActivities();
 
-        List<HardConstraint> failedActivityConstraints = new ArrayList<>();
+        List<String> failedActivityConstraints = new ArrayList<>();
         while (!tourEnd) {
             TourActivity nextAct;
             if (i < activities.size()) {
@@ -229,9 +228,7 @@ final class ShipmentInsertionCalculator extends AbstractInsertionCalculator {
         }
         if (pickupInsertionIndex == InsertionData.NO_INDEX) {
             InsertionData emptyInsertionData = new InsertionData.NoInsertionFound();
-            for (HardConstraint failed : failedActivityConstraints) {
-                emptyInsertionData.addFailedConstrainName(failed.getClass().getSimpleName());
-            }
+            emptyInsertionData.getFailedConstraintNames().addAll(failedActivityConstraints);
             return emptyInsertionData;
         }
         InsertionData insertionData = new InsertionData(bestCost, pickupInsertionIndex, deliveryInsertionIndex, newVehicle, newDriver);
diff --git a/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/ShipmentInsertionCalculatorFlex.java b/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/ShipmentInsertionCalculatorFlex.java
index 8862481a..b490b246 100644
--- a/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/ShipmentInsertionCalculatorFlex.java
+++ b/jsprit-core/src/main/java/com/graphhopper/jsprit/core/algorithm/recreate/ShipmentInsertionCalculatorFlex.java
@@ -20,7 +20,6 @@ package com.graphhopper.jsprit.core.algorithm.recreate;
 import com.graphhopper.jsprit.core.problem.JobActivityFactory;
 import com.graphhopper.jsprit.core.problem.constraint.ConstraintManager;
 import com.graphhopper.jsprit.core.problem.constraint.HardActivityConstraint.ConstraintsStatus;
-import com.graphhopper.jsprit.core.problem.constraint.HardConstraint;
 import com.graphhopper.jsprit.core.problem.constraint.SoftActivityConstraint;
 import com.graphhopper.jsprit.core.problem.constraint.SoftRouteConstraint;
 import com.graphhopper.jsprit.core.problem.cost.VehicleRoutingActivityCosts;
@@ -147,7 +146,7 @@ public final class ShipmentInsertionCalculatorFlex extends AbstractInsertionCalc
         //pickupShipmentLoop
         List<TourActivity> activities = currentRoute.getTourActivities().getActivities();
 
-        List<HardConstraint> failedActivityConstraints = new ArrayList<>();
+        List<String> failedActivityConstraints = new ArrayList<>();
         while (!tourEnd) {
             TourActivity nextAct;
             if (i < activities.size()) {
@@ -253,9 +252,7 @@ public final class ShipmentInsertionCalculatorFlex extends AbstractInsertionCalc
 
         if (pickupInsertionIndex == InsertionData.NO_INDEX) {
             InsertionData emptyInsertionData = new InsertionData.NoInsertionFound();
-            for (HardConstraint failed : failedActivityConstraints) {
-                emptyInsertionData.addFailedConstrainName(failed.getClass().getSimpleName());
-            }
+            emptyInsertionData.getFailedConstraintNames().addAll(failedActivityConstraints);
             return emptyInsertionData;
         }
         InsertionData insertionData = new InsertionData(bestCost, pickupInsertionIndex, deliveryInsertionIndex, newVehicle, newDriver);