diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/data/criticalpath/CriticalPathCalculator.java b/ganttzk/src/main/java/org/zkoss/ganttz/data/criticalpath/CriticalPathCalculator.java
index 0b932c098..17e0420c9 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/data/criticalpath/CriticalPathCalculator.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/data/criticalpath/CriticalPathCalculator.java
@@ -264,7 +264,7 @@ public class CriticalPathCalculator<T, D extends IDependency<T>> {
                 Node<T, D> node = nodes.get(task);
                 DependencyType dependencyType = getDependencyTypeEndStartByDefault(
                         currentTask, task);
-                Constraint<GanttDate> constraint = getDateStartConstraint(task);
+                Constraint<GanttDate> constraint = getDateConstraints(task);
 
                 switch (dependencyType) {
                 case START_START:
@@ -303,30 +303,26 @@ public class CriticalPathCalculator<T, D extends IDependency<T>> {
         node.setEarliestStart(earliestStart);
     }
 
-    private Constraint<GanttDate> getDateStartConstraint(T task) {
+    private Constraint<GanttDate> getDateConstraints(T task) {
         if (task == null) {
             return null;
         }
 
-        List<Constraint<GanttDate>> constraints = graph
+        List<Constraint<GanttDate>> startConstraints = graph
                 .getStartConstraintsFor(task);
-        if (constraints == null) {
-            return null;
-        }
-        return Constraint.coalesce(constraints);
-    }
-
-    private Constraint<GanttDate> getDateEndConstraint(T task) {
-        if (task == null) {
-            return null;
-        }
-
-        List<Constraint<GanttDate>> constraints = graph
+        List<Constraint<GanttDate>> endConstraints = graph
                 .getEndConstraintsFor(task);
-        if (constraints == null) {
+        if ((startConstraints == null) && (endConstraints == null)) {
             return null;
         }
-        return Constraint.coalesce(constraints);
+        if (startConstraints == null) {
+            return Constraint.coalesce(endConstraints);
+        }
+        if (endConstraints == null) {
+            return Constraint.coalesce(startConstraints);
+        }
+        startConstraints.addAll(endConstraints);
+        return Constraint.coalesce(startConstraints);
     }
 
     private void backward(Node<T, D> currentNode, T nextTask) {
@@ -352,7 +348,7 @@ public class CriticalPathCalculator<T, D extends IDependency<T>> {
                 Node<T, D> node = nodes.get(task);
                 DependencyType dependencyType = getDependencyTypeEndStartByDefault(
                         task, currentTask);
-                Constraint<GanttDate> constraint = getDateEndConstraint(task);
+                Constraint<GanttDate> constraint = getDateConstraints(task);
 
                 switch (dependencyType) {
                 case START_START: