diff --git a/libreplan-business/src/main/java/org/libreplan/business/costcategories/daos/TypeOfWorkHoursDAO.java b/libreplan-business/src/main/java/org/libreplan/business/costcategories/daos/TypeOfWorkHoursDAO.java
index 587aa4016..4ed9ede03 100644
--- a/libreplan-business/src/main/java/org/libreplan/business/costcategories/daos/TypeOfWorkHoursDAO.java
+++ b/libreplan-business/src/main/java/org/libreplan/business/costcategories/daos/TypeOfWorkHoursDAO.java
@@ -28,12 +28,15 @@ import org.apache.commons.lang.Validate;
 import org.hibernate.Criteria;
 import org.hibernate.criterion.Order;
 import org.hibernate.criterion.Restrictions;
+import org.libreplan.business.common.daos.IConfigurationDAO;
 import org.libreplan.business.common.daos.IntegrationEntityDAO;
+import org.libreplan.business.common.entities.Configuration;
 import org.libreplan.business.common.exceptions.InstanceNotFoundException;
 import org.libreplan.business.common.exceptions.ValidationException;
 import org.libreplan.business.costcategories.entities.HourCost;
 import org.libreplan.business.costcategories.entities.TypeOfWorkHours;
 import org.libreplan.business.workreports.entities.WorkReportLine;
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.context.annotation.Scope;
 import org.springframework.stereotype.Repository;
@@ -50,6 +53,9 @@ public class TypeOfWorkHoursDAO extends IntegrationEntityDAO<TypeOfWorkHours>
         implements
         ITypeOfWorkHoursDAO {
 
+    @Autowired
+    private IConfigurationDAO configurationDAO;
+
     @Override
     public TypeOfWorkHours findUniqueByCode(TypeOfWorkHours typeOfWorkHours)
             throws InstanceNotFoundException {
@@ -142,6 +148,7 @@ public class TypeOfWorkHoursDAO extends IntegrationEntityDAO<TypeOfWorkHours>
     public void checkIsReferencedByOtherEntities(TypeOfWorkHours type) throws ValidationException {
         checkHasHourCost(type);
         checkHasWorkReportLine(type);
+        checkIsMonthlyTimesheetsTypeOfWorkHours(type);
     }
 
     private void checkHasWorkReportLine(TypeOfWorkHours type) {
@@ -167,6 +174,17 @@ public class TypeOfWorkHoursDAO extends IntegrationEntityDAO<TypeOfWorkHours>
         }
     }
 
+    private void checkIsMonthlyTimesheetsTypeOfWorkHours(TypeOfWorkHours type) {
+        Configuration configuration = configurationDAO.getConfiguration();
+        if (configuration.getMonthlyTimesheetsTypeOfWorkHours().getId()
+                .equals(type.getId())) {
+            throw ValidationException
+                    .invalidValue(
+                            "Cannot delete the type of work hours. It is configured as type of work hours for monthly timesheets.",
+                            type);
+        }
+    }
+
     @Override
     public boolean existsByName(TypeOfWorkHours typeOfWorkHours) {
         Criteria c = getSession().createCriteria(TypeOfWorkHours.class).add(
diff --git a/libreplan-business/src/main/java/org/libreplan/business/costcategories/entities/TypeOfWorkHours.java b/libreplan-business/src/main/java/org/libreplan/business/costcategories/entities/TypeOfWorkHours.java
index d799e910c..c82024096 100644
--- a/libreplan-business/src/main/java/org/libreplan/business/costcategories/entities/TypeOfWorkHours.java
+++ b/libreplan-business/src/main/java/org/libreplan/business/costcategories/entities/TypeOfWorkHours.java
@@ -143,6 +143,19 @@ public class TypeOfWorkHours extends IntegrationEntity implements IHumanIdentifi
         }
     }
 
+    @AssertTrue(message = "the type of work hours for monthly timesheets cannot be disabled")
+    public boolean checkMonthlyTimesheetsTypeOfWorkHoursNotDisabled() {
+        if (!isNewObject() && !getEnabled()) {
+            TypeOfWorkHours typeOfWorkHours = Registry.getConfigurationDAO()
+                    .getConfiguration().getMonthlyTimesheetsTypeOfWorkHours();
+            if (typeOfWorkHours.getId().equals(getId())) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
     public String toString() {
         return name;
     }