diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/FlatFunction.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/FlatFunction.java
deleted file mode 100644
index 73f958bed..000000000
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/FlatFunction.java
+++ /dev/null
@@ -1,71 +0,0 @@
-/*
- * This file is part of NavalPlan
- *
- * Copyright (C) 2009-2010 Fundación para o Fomento da Calidade Industrial e
- *                         Desenvolvemento Tecnolóxico de Galicia
- * Copyright (C) 2010-2011 Igalia, S.L.
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-
-package org.navalplanner.business.planner.entities;
-
-import java.util.Arrays;
-import java.util.List;
-
-import org.navalplanner.business.planner.entities.allocationalgorithms.ResourcesPerDayModification;
-import org.navalplanner.business.workingday.EffortDuration;
-
-/**
- * Calculate hours per day for resource based on total amount of hours to be
- * done and number of resources per day using a flat allocation
- *
- * @author Diego Pino García <dpino@igalia.com>
- */
-public class FlatFunction extends AssignmentFunction {
-
-    public static FlatFunction create() {
-        return create(new FlatFunction());
-    }
-
-    protected FlatFunction() {
-
-    }
-
-    public String getName() {
-        return AssignmentFunctionName.FLAT.toString();
-    }
-
-
-    public void applyTo(ResourceAllocation<?> resourceAllocation) {
-        apply(resourceAllocation);
-    }
-
-    private void apply(ResourceAllocation<?> resourceAllocation) {
-        int hours = resourceAllocation.getAssignedHours();
-
-        List<ResourcesPerDayModification> resourcesPerDayModification = Arrays.asList(resourceAllocation
-                    .asResourcesPerDayModification());
-
-        ResourceAllocation
-            .allocating(resourcesPerDayModification)
-            .untilAllocating(EffortDuration.hours(hours));
-    }
-
-    @Override
-    public boolean isManual() {
-        return false;
-    }
-
-}
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/ResourceAllocation.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/ResourceAllocation.java
index 25b251ae7..ec5c73b12 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/ResourceAllocation.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/ResourceAllocation.java
@@ -87,8 +87,6 @@ public abstract class ResourceAllocation<T extends DayAssignment> extends
 
     private static final Log LOG = LogFactory.getLog(ResourceAllocation.class);
 
-    private static final FlatFunction FLAT_FUNCTION = FlatFunction.create();
-
     public static <T extends ResourceAllocation<?>> List<T> getSatisfied(
             Collection<T> resourceAllocations) {
         Validate.notNull(resourceAllocations);
@@ -1418,16 +1416,17 @@ public abstract class ResourceAllocation<T extends DayAssignment> extends
         return assignmentFunction;
     }
 
-    public void setAssignmentFunction(AssignmentFunction assignmentFunction) {
-        // If the assignment function is empty, avoid creating an association
-        // between the resource allocation and the assignment function
-        if (assignmentFunction == null) {
-            this.assignmentFunction = null;
-            FLAT_FUNCTION.applyTo(this);
-            return;
-        }
+    /**
+     * If {@link AssignmentFunction} is null, it's just set and nothing is
+     * applied
+     *
+     * @param assignmentFunction
+     */
+    public void setAssignmentFunctionAndApplyIfNotFlat(AssignmentFunction assignmentFunction) {
         this.assignmentFunction = assignmentFunction;
-        this.assignmentFunction.applyTo(this);
+        if (this.assignmentFunction != null) {
+            this.assignmentFunction.applyTo(this);
+        }
     }
 
     public void setAssignmentFunctionWithoutApply(AssignmentFunction assignmentFunction) {
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/AdvancedAllocationController.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/AdvancedAllocationController.java
index 303085224..5fed9ec51 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/AdvancedAllocationController.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/AdvancedAllocationController.java
@@ -1388,7 +1388,7 @@ class Row {
 
         @Override
         public void applyOn(ResourceAllocation<?> resourceAllocation) {
-            resourceAllocation.setAssignmentFunction(ManualFunction.create());
+            resourceAllocation.setAssignmentFunctionAndApplyIfNotFlat(ManualFunction.create());
         }
 
         @Override
@@ -1490,7 +1490,7 @@ class Row {
         @Override
         public void applyOn(
                 ResourceAllocation<?> resourceAllocation) {
-            resourceAllocation.setAssignmentFunction(SigmoidFunction.create());
+            resourceAllocation.setAssignmentFunctionAndApplyIfNotFlat(SigmoidFunction.create());
             reloadEfforts();
         }
 
@@ -1655,7 +1655,7 @@ class Row {
                 .setSelectedFunction(AssignmentFunctionName.MANUAL.toString());
         ResourceAllocation<?> allocation = getAllocation();
         if (!(allocation.getAssignmentFunction() instanceof ManualFunction)) {
-            allocation.setAssignmentFunction(ManualFunction.create());
+            allocation.setAssignmentFunctionAndApplyIfNotFlat(ManualFunction.create());
         }
     }
 
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/streches/StrechesFunctionConfiguration.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/streches/StrechesFunctionConfiguration.java
index 73c514f38..704531035 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/streches/StrechesFunctionConfiguration.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/streches/StrechesFunctionConfiguration.java
@@ -58,7 +58,7 @@ public abstract class StrechesFunctionConfiguration implements
 
         int exitStatus = stretchesFunctionController.showWindow();
         if (exitStatus == Messagebox.OK) {
-            getAllocation().setAssignmentFunction(
+            getAllocation().setAssignmentFunctionAndApplyIfNotFlat(
                     stretchesFunctionController.getAssignmentFunction());
             assignmentFunctionChanged();
         }
@@ -94,7 +94,7 @@ public abstract class StrechesFunctionConfiguration implements
 
     @Override
     public void applyOn(ResourceAllocation<?> resourceAllocation) {
-        resourceAllocation.setAssignmentFunction(StretchesFunction.create());
+        resourceAllocation.setAssignmentFunctionAndApplyIfNotFlat(StretchesFunction.create());
     }
 
     @Override