diff --git a/workflow.module b/workflow.module
index 96d63f0..9fa07ca 100644
--- a/workflow.module
+++ b/workflow.module
@@ -749,6 +749,14 @@ function workflow_execute_transition($node, $sid, $comment = NULL, $force = FALS
   if (empty($node->nid)) {
     return;
   }
+  
+  // Make sure this transition is allowed.
+  $result = module_invoke_all('workflow', 'transition permitted', $current_sid, $transition->state_id, $node);
+  // Did anybody veto this choice?
+  if (in_array(FALSE, $result)) {
+    // If vetoed, quit.
+    return;
+  }
 
   $old_sid = workflow_node_current_state($node);