diff --git a/source/java/org/alfresco/repo/workflow/jbpm/JBPMEngine.java b/source/java/org/alfresco/repo/workflow/jbpm/JBPMEngine.java
index 2b090fafde..10d8e72487 100644
--- a/source/java/org/alfresco/repo/workflow/jbpm/JBPMEngine.java
+++ b/source/java/org/alfresco/repo/workflow/jbpm/JBPMEngine.java
@@ -1501,7 +1501,12 @@ public class JBPMEngine extends BPMEngine
                     {
                         throw new WorkflowException("Task owner '" + value + "' is invalid");
                     }
-                    instance.setActorId((String)value);
+                    String actorId = (String)value;
+                    String existingActorId = instance.getActorId();
+                    if (existingActorId == null || !actorId.equals(existingActorId))
+                    {
+                        instance.setActorId((String)value);
+                    }
                     continue;
                 }
             }
diff --git a/source/java/org/alfresco/repo/workflow/jbpm/test_taskassign.xml b/source/java/org/alfresco/repo/workflow/jbpm/test_taskassign.xml
new file mode 100644
index 0000000000..0af8c39c25
--- /dev/null
+++ b/source/java/org/alfresco/repo/workflow/jbpm/test_taskassign.xml
@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<process-definition xmlns="urn:jbpm.org:jpdl-3.1" name="wf:testtaskassign">
+
+    <swimlane name="initiator" />
+
+    <start-state name="start">
+        <task name="bpm:startTask" swimlane="initiator" />
+        <transition name="" to="assign" />
+    </start-state>
+
+    <swimlane name="assignee">
+        <assignment class="org.alfresco.repo.workflow.jbpm.AlfrescoAssignment">
+           <actor>#{bpm_assignee}</actor>
+        </assignment>
+    </swimlane>
+
+    <task-node name="assign">
+        <task name="wf:workflowTask" swimlane="assignee">
+           <event type="task-assign">
+              <script>
+                System.out.println("Task assigned: " + executionContext.getTaskInstance().getActorId());
+              </script>
+           </event>
+        </task>
+        <transition name="" to="end" />
+    </task-node>
+
+    <end-state name="end" />
+
+</process-definition>
\ No newline at end of file