diff --git a/source/java/org/alfresco/repo/workflow/WorkflowServiceImpl.java b/source/java/org/alfresco/repo/workflow/WorkflowServiceImpl.java
index f5b95261ae..84d6f9ba63 100644
--- a/source/java/org/alfresco/repo/workflow/WorkflowServiceImpl.java
+++ b/source/java/org/alfresco/repo/workflow/WorkflowServiceImpl.java
@@ -622,7 +622,12 @@ public class WorkflowServiceImpl implements WorkflowService
      */
     public List<WorkflowInstance> cancelWorkflows(List<String> workflowIds)
     {
-        if (logger.isTraceEnabled()) { logger.trace("Cancelling " + (workflowIds == null ? 0 : workflowIds.size()) + " workflowIds..."); }
+        if (workflowIds == null)
+        {
+            workflowIds = Collections.emptyList();
+        }
+        
+        if (logger.isTraceEnabled()) { logger.trace("Cancelling " + workflowIds.size() + " workflowIds..."); }
         
         List<WorkflowInstance> result = new ArrayList<WorkflowInstance>(workflowIds.size());