diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/FormBinder.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/FormBinder.java
index 2f8cc764e..e038c24da 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/FormBinder.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/FormBinder.java
@@ -1,11 +1,14 @@
 package org.navalplanner.web.planner.allocation;
 
+import static org.navalplanner.web.I18nHelper._;
+
 import java.util.HashMap;
 import java.util.Map;
 
 import org.navalplanner.business.planner.entities.AggregateOfResourceAllocations;
 import org.navalplanner.business.planner.entities.CalculatedValue;
 import org.zkoss.zk.ui.Component;
+import org.zkoss.zk.ui.WrongValueException;
 import org.zkoss.zk.ui.event.Event;
 import org.zkoss.zk.ui.event.EventListener;
 import org.zkoss.zk.ui.event.Events;
@@ -178,4 +181,12 @@ class FormBinder {
         applyButton.setDisabled(false);
     }
 
+    public void markGenericAllocationMustBeNoZeroOrMoreAllocations(
+            AllocationDTO allocation) {
+        Decimalbox decimalbox = resourcesPerDayInputsByAllocationDTO
+                .get(allocation);
+        throw new WrongValueException(decimalbox,
+                _("it must be no zero or must add more allocations"));
+    }
+
 }
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/ResourceAllocationsBeingEdited.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/ResourceAllocationsBeingEdited.java
index 987ed4ef2..a5dc199b6 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/ResourceAllocationsBeingEdited.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/ResourceAllocationsBeingEdited.java
@@ -119,7 +119,22 @@ public class ResourceAllocationsBeingEdited {
         return result;
     }
 
+    public void checkInvalidValues() {
+        if (thereIsJustOneEmptyGenericResourceAllocation()) {
+            formBinder
+                    .markGenericAllocationMustBeNoZeroOrMoreAllocations(currentAllocations
+                            .get(0));
+        }
+    }
+
+    private boolean thereIsJustOneEmptyGenericResourceAllocation() {
+        return currentAllocations.size() == 1
+                && currentAllocations.get(0).isGeneric()
+                && currentAllocations.get(0).isEmptyResourcesPerDay();
+    }
+
     public AggregateOfResourceAllocations doAllocation() {
+        checkInvalidValues();
         List<ResourceAllocationWithDesiredResourcesPerDay> allocations = asResourceAllocations();
         switch (calculatedValue) {
         case NUMBER_OF_HOURS: