diff --git a/lib/taskana-core/src/main/java/pro/taskana/impl/TaskMonitorServiceImpl.java b/lib/taskana-core/src/main/java/pro/taskana/impl/TaskMonitorServiceImpl.java
index 64738f365..0704bcb99 100644
--- a/lib/taskana-core/src/main/java/pro/taskana/impl/TaskMonitorServiceImpl.java
+++ b/lib/taskana-core/src/main/java/pro/taskana/impl/TaskMonitorServiceImpl.java
@@ -76,11 +76,7 @@ public class TaskMonitorServiceImpl implements TaskMonitorService {
             List<MonitorQueryItem> monitorQueryItems = taskMonitorMapper.getTaskCountOfWorkbaskets(
                 workbasketIds, states, categories, domains, customField, customFieldValues);
 
-            if (inWorkingDays) {
-                report.addItems(monitorQueryItems, new DaysToWorkingDaysPreProcessor<>(columnHeaders));
-            } else {
-                report.addItems(monitorQueryItems);
-            }
+            report.addItems(monitorQueryItems, new DaysToWorkingDaysPreProcessor<>(columnHeaders, inWorkingDays));
 
             return report;
 
@@ -127,11 +123,7 @@ public class TaskMonitorServiceImpl implements TaskMonitorService {
             List<MonitorQueryItem> monitorQueryItems = taskMonitorMapper.getTaskCountOfCategories(
                 workbasketIds, states, categories, domains, customField, customFieldValues);
 
-            if (inWorkingDays) {
-                report.addItems(monitorQueryItems, new DaysToWorkingDaysPreProcessor<>(columnHeaders));
-            } else {
-                report.addItems(monitorQueryItems);
-            }
+            report.addItems(monitorQueryItems, new DaysToWorkingDaysPreProcessor<>(columnHeaders, inWorkingDays));
 
             return report;
 
@@ -179,11 +171,7 @@ public class TaskMonitorServiceImpl implements TaskMonitorService {
             List<MonitorQueryItem> monitorQueryItems = taskMonitorMapper.getTaskCountOfClassifications(
                 workbasketIds, states, categories, domains, customField, customFieldValues);
 
-            if (inWorkingDays) {
-                report.addItems(monitorQueryItems, new DaysToWorkingDaysPreProcessor<>(columnHeaders));
-            } else {
-                report.addItems(monitorQueryItems);
-            }
+            report.addItems(monitorQueryItems, new DaysToWorkingDaysPreProcessor<>(columnHeaders, inWorkingDays));
 
             return report;
 
@@ -234,11 +222,8 @@ public class TaskMonitorServiceImpl implements TaskMonitorService {
                 .getTaskCountOfDetailedClassifications(workbasketIds, states, categories, domains, customField,
                     customFieldValues);
 
-            if (inWorkingDays) {
-                report.addItems(detailedMonitorQueryItems, new DaysToWorkingDaysPreProcessor<>(columnHeaders));
-            } else {
-                report.addItems(detailedMonitorQueryItems);
-            }
+            report.addItems(detailedMonitorQueryItems,
+                new DaysToWorkingDaysPreProcessor<>(columnHeaders, inWorkingDays));
 
             return report;
 
@@ -290,11 +275,7 @@ public class TaskMonitorServiceImpl implements TaskMonitorService {
             List<MonitorQueryItem> monitorQueryItems = taskMonitorMapper.getTaskCountOfCustomFieldValues(
                 workbasketIds, states, categories, domains, customField, customFieldValues);
 
-            if (inWorkingDays) {
-                report.addItems(monitorQueryItems, new DaysToWorkingDaysPreProcessor<>(columnHeaders));
-            } else {
-                report.addItems(monitorQueryItems);
-            }
+            report.addItems(monitorQueryItems, new DaysToWorkingDaysPreProcessor<>(columnHeaders, inWorkingDays));
 
             return report;
 
diff --git a/lib/taskana-core/src/main/java/pro/taskana/impl/report/impl/DaysToWorkingDaysPreProcessor.java b/lib/taskana-core/src/main/java/pro/taskana/impl/report/impl/DaysToWorkingDaysPreProcessor.java
index 238b0c85b..cb5879eac 100644
--- a/lib/taskana-core/src/main/java/pro/taskana/impl/report/impl/DaysToWorkingDaysPreProcessor.java
+++ b/lib/taskana-core/src/main/java/pro/taskana/impl/report/impl/DaysToWorkingDaysPreProcessor.java
@@ -14,14 +14,18 @@ public class DaysToWorkingDaysPreProcessor<Item extends MonitorQueryItem> implem
 
     private DaysToWorkingDaysConverter instance;
 
-    public DaysToWorkingDaysPreProcessor(List<TimeIntervalColumnHeader> columnHeaders)
+    public DaysToWorkingDaysPreProcessor(List<TimeIntervalColumnHeader> columnHeaders, boolean activate)
         throws InvalidArgumentException {
-        instance = DaysToWorkingDaysConverter.initialize(columnHeaders);
+        if (activate) {
+            instance = DaysToWorkingDaysConverter.initialize(columnHeaders);
+        }
     }
 
     @Override
     public Item apply(Item item) {
-        item.setAgeInDays(instance.convertDaysToWorkingDays(item.getAgeInDays()));
+        if (instance != null) {
+            item.setAgeInDays(instance.convertDaysToWorkingDays(item.getAgeInDays()));
+        }
         return item;
     }
 }
diff --git a/lib/taskana-core/src/test/java/pro/taskana/impl/TaskMonitorServiceImplTest.java b/lib/taskana-core/src/test/java/pro/taskana/impl/TaskMonitorServiceImplTest.java
index 1a3432bc7..8fedddf39 100644
--- a/lib/taskana-core/src/test/java/pro/taskana/impl/TaskMonitorServiceImplTest.java
+++ b/lib/taskana-core/src/test/java/pro/taskana/impl/TaskMonitorServiceImplTest.java
@@ -82,8 +82,7 @@ public class TaskMonitorServiceImplTest {
             categories, domains, customField, customFieldValues);
 
         WorkbasketLevelReport actualResult = cut.getWorkbasketLevelReport(workbasketIds, states, categories, domains,
-            customField,
-            customFieldValues);
+            customField, customFieldValues);
 
         verify(taskanaEngineImplMock, times(1)).openConnection();
         verify(taskanaEngineImplMock, times(2)).getConfiguration();
@@ -121,8 +120,7 @@ public class TaskMonitorServiceImplTest {
             categories, domains, customField, customFieldValues);
 
         WorkbasketLevelReport actualResult = cut.getWorkbasketLevelReport(workbasketIds, states, categories, domains,
-            customField,
-            customFieldValues, reportLineItemDefinitions);
+            customField, customFieldValues, reportLineItemDefinitions);
 
         verify(taskanaEngineImplMock, times(1)).openConnection();
         verify(taskanaEngineImplMock, times(2)).getConfiguration();
@@ -157,8 +155,7 @@ public class TaskMonitorServiceImplTest {
             domains, customField, customFieldValues);
 
         CategoryReport actualResult = cut.getCategoryReport(workbasketIds, states, categories, domains,
-            customField,
-            customFieldValues);
+            customField, customFieldValues);
 
         verify(taskanaEngineImplMock, times(1)).openConnection();
         verify(taskanaEngineImplMock, times(2)).getConfiguration();
@@ -194,8 +191,7 @@ public class TaskMonitorServiceImplTest {
             domains, customField, customFieldValues);
 
         CategoryReport actualResult = cut.getCategoryReport(workbasketIds, states, categories, domains,
-            customField,
-            customFieldValues, reportLineItemDefinitions);
+            customField, customFieldValues, reportLineItemDefinitions);
 
         verify(taskanaEngineImplMock, times(1)).openConnection();
         verify(taskanaEngineImplMock, times(2)).getConfiguration();