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 096ea268c..dfef35a18 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
@@ -113,6 +113,12 @@ public abstract class ResourceAllocation<T extends DayAssignment> extends
             @Override
             public int compare(ResourceAllocation<?> o1,
                     ResourceAllocation<?> o2) {
+                if (o1.getStartDate() == null) {
+                    return -1;
+                }
+                if (o2.getStartDate() == null) {
+                    return 1;
+                }
                 return o1.getStartDate().compareTo(o2.getStartDate());
             }
         };