diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Task.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Task.java
index cc4c06436..c2acb3c13 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Task.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/Task.java
@@ -368,6 +368,9 @@ public class Task extends TaskElement {
             @Override
             public Collection<Worker> findWorkersMatching(
                     Collection<? extends Criterion> requiredCriterions) {
+                if (requiredCriterions.isEmpty()) {
+                    return new ArrayList<Worker>();
+                }
                 Collection<Worker> result = new ArrayList<Worker>();
                 for (Worker each : allWorkers) {
                     if (each.satisfiesCriterions(requiredCriterions)) {
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/ResourceAllocationModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/ResourceAllocationModel.java
index b217d204a..e55163a12 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/ResourceAllocationModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/planner/allocation/ResourceAllocationModel.java
@@ -234,10 +234,15 @@ public class ResourceAllocationModel implements IResourceAllocationModel {
             public Collection<Worker> findWorkersMatching(
                     Collection<? extends Criterion> requiredCriterions) {
                 reassociateResourcesWithSession();
-                List<Resource> findAllSatisfyingCriterions = resourceDAO
-                        .findAllSatisfyingCriterions(requiredCriterions);
+                List<Resource> allSatisfyingCriterions;
+                if (!requiredCriterions.isEmpty()) {
+                    allSatisfyingCriterions = resourceDAO
+                            .findAllSatisfyingCriterions(requiredCriterions);
+                } else {
+                    allSatisfyingCriterions = new ArrayList<Resource>();
+                }
                 return Resource.workers(reloadResources(Resource
-                        .workers(findAllSatisfyingCriterions)));
+                        .workers(allSatisfyingCriterions)));
             }
         };
     }