diff --git a/src/nodes/sub_workflow.php b/src/nodes/sub_workflow.php
index a50bf24..5017f99 100644
--- a/src/nodes/sub_workflow.php
+++ b/src/nodes/sub_workflow.php
@@ -163,7 +163,16 @@ public function execute( ezcWorkflowExecution $execution )
             {
                 $subExecution = $execution->getSubExecution( $this->state );
                 $subExecution->workflow = $workflow;
-                $subExecution->resume( $execution->getVariables() );
+
+                $subVariables = [];
+                foreach ( $execution->getVariables() as $variableName => $data )
+                {
+                    if ( isset($this->configuration['variables']['in'][$variableName]) )
+                    {
+                        $subVariables[$this->configuration['variables']['in'][$variableName]] = $data;
+                    }
+                }
+                $subExecution->resume( $subVariables );
             }
         }
 
@@ -188,9 +197,10 @@ public function execute( ezcWorkflowExecution $execution )
         }
 
         // Execution of Sub Workflow has been suspended.
+        $reverseInVariableMap = array_flip( $this->configuration['variables']['in'] );
         foreach ( $subExecution->getWaitingFor() as $variableName => $data )
         {
-            $execution->addWaitingFor( $this, $variableName, $data['condition'] );
+            $execution->addWaitingFor( $this, $reverseInVariableMap[$variableName], $data['condition'] );
         }
 
         return false;
@@ -298,7 +308,9 @@ protected function passVariables( ezcWorkflowExecution $from, ezcWorkflowExecuti
     {
         foreach ( $variables as $fromName => $toName )
         {
-            $to->setVariable( $toName, $from->getVariable( $fromName ) );
+            if ( $from->hasVariable( $fromName ) ) {
+                $to->setVariable( $toName, $from->getVariable( $fromName ) );
+            }
         }
     }
 }