diff --git a/config/alfresco/workflow/workflow-messages.properties b/config/alfresco/workflow/workflow-messages.properties
index f73fa27f23..6de7494b68 100644
--- a/config/alfresco/workflow/workflow-messages.properties
+++ b/config/alfresco/workflow/workflow-messages.properties
@@ -229,3 +229,4 @@ listconstraint.wf_reviewOutcomeOptions.Reject=Reject
 workflowtask.outcome.Approve=Approved
 workflowtask.outcome.Reject=Rejected
 
+workflowtask.already.done.error=This task has already been completed and is no longer editable.
diff --git a/source/java/org/alfresco/repo/forms/processor/workflow/TaskFormPersister.java b/source/java/org/alfresco/repo/forms/processor/workflow/TaskFormPersister.java
index 2e60c509b5..62f27d18d4 100644
--- a/source/java/org/alfresco/repo/forms/processor/workflow/TaskFormPersister.java
+++ b/source/java/org/alfresco/repo/forms/processor/workflow/TaskFormPersister.java
@@ -22,6 +22,7 @@ package org.alfresco.repo.forms.processor.workflow;
 import java.io.Serializable;
 import java.util.List;
 
+import org.alfresco.error.AlfrescoRuntimeException;
 import org.alfresco.repo.forms.FormData.FieldData;
 import org.alfresco.repo.forms.processor.node.ContentModelItemData;
 import org.alfresco.repo.policy.BehaviourFilter;
@@ -33,6 +34,7 @@ import org.alfresco.service.cmr.repository.NodeService;
 import org.alfresco.service.cmr.security.AuthenticationService;
 import org.alfresco.service.cmr.workflow.WorkflowService;
 import org.alfresco.service.cmr.workflow.WorkflowTask;
+import org.alfresco.service.cmr.workflow.WorkflowTaskState;
 import org.alfresco.service.namespace.NamespaceService;
 import org.alfresco.service.namespace.QName;
 import org.apache.commons.logging.Log;
@@ -58,7 +60,13 @@ public class TaskFormPersister extends ContentModelFormPersister<WorkflowTask>
     {
         super(itemData, namespaceService, dictionaryService, logger);
         WorkflowTask item = itemData.getItem();
-        
+
+        // make sure that the task is not already completed
+        if (item.getState().equals(WorkflowTaskState.COMPLETED))
+        {
+            throw new AlfrescoRuntimeException("workflowtask.already.done.error");
+        }
+
         // make sure the current user is able to edit the task
         if (!workflowService.isTaskEditable(item, authenticationService.getCurrentUserName()))
         {