Index: engine/src/test/java/org/camunda/bpm/engine/test/bpmn/multiinstance/DelegateBean.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- engine/src/test/java/org/camunda/bpm/engine/test/bpmn/multiinstance/DelegateBean.java	(revision 13396e10cc0801825458604bd2ee22f2799e5d48)
+++ engine/src/test/java/org/camunda/bpm/engine/test/bpmn/multiinstance/DelegateBean.java	(revision )
@@ -32,6 +32,6 @@
   public List<String> resolveCollection(DelegateExecution delegateExecution) {
 
     DelegateEvent.recordEventFor(delegateExecution);
-    return Arrays.asList("1");
+    return Arrays.asList("1", "2", "3");
   }
 }
Index: engine/src/test/java/org/camunda/bpm/engine/test/bpmn/multiinstance/SubEvent.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- engine/src/test/java/org/camunda/bpm/engine/test/bpmn/multiinstance/SubEvent.java	(revision )
+++ engine/src/test/java/org/camunda/bpm/engine/test/bpmn/multiinstance/SubEvent.java	(revision )
@@ -0,0 +1,330 @@
+/* Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.camunda.bpm.engine.test.bpmn.multiinstance;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+import org.camunda.bpm.engine.ProcessEngineServices;
+import org.camunda.bpm.engine.delegate.DelegateExecution;
+import org.camunda.bpm.engine.variable.VariableMap;
+import org.camunda.bpm.engine.variable.value.TypedValue;
+import org.camunda.bpm.model.bpmn.BpmnModelInstance;
+import org.camunda.bpm.model.bpmn.instance.FlowElement;
+
+/**
+ * @author Thorben Lindhauer
+ *
+ */
+public class SubEvent implements DelegateExecution {
+
+  protected static final List<SubEvent> RECORDED_EVENTS = new ArrayList<SubEvent>();
+
+  protected String activityInstanceId;
+  protected String businessKey;
+  protected String currentActivityId;
+  protected String currentActivityName;
+  protected String currentTransitionId;
+  protected String eventName;
+  protected String id;
+  protected String parentActivityInstanceId;
+  protected String parentId;
+  protected String processBusinessKey;
+  protected String processDefinitionId;
+  protected String processInstanceId;
+  protected String tenantId;
+  protected String variableScopeKey;
+
+  public static SubEvent fromExecution(DelegateExecution delegateExecution) {
+    SubEvent event = new SubEvent();
+
+    event.activityInstanceId = delegateExecution.getActivityInstanceId();
+    event.businessKey = delegateExecution.getBusinessKey();
+    event.currentActivityId = delegateExecution.getCurrentActivityId();
+    event.currentActivityName = delegateExecution.getCurrentActivityName();
+    event.currentTransitionId = delegateExecution.getCurrentTransitionId();
+    event.eventName = delegateExecution.getEventName();
+    event.id = delegateExecution.getId();
+    event.parentActivityInstanceId = delegateExecution.getParentActivityInstanceId();
+    event.parentId = delegateExecution.getParentId();
+    event.processBusinessKey = delegateExecution.getProcessBusinessKey();
+    event.processDefinitionId = delegateExecution.getProcessDefinitionId();
+    event.processInstanceId = delegateExecution.getProcessInstanceId();
+    event.tenantId = delegateExecution.getTenantId();
+    event.variableScopeKey = delegateExecution.getVariableScopeKey();
+
+    return event;
+  }
+
+  public static void clearEvents() {
+    RECORDED_EVENTS.clear();
+  }
+
+  public static void recordEventFor(DelegateExecution execution) {
+    RECORDED_EVENTS.add(SubEvent.fromExecution(execution));
+  }
+
+  public static List<SubEvent> getEvents() {
+    return RECORDED_EVENTS;
+  }
+
+  @Override
+  public String getId() {
+    return id;
+  }
+
+  @Override
+  public String getEventName() {
+    return eventName;
+  }
+
+  @Override
+  public String getBusinessKey() {
+    return businessKey;
+  }
+
+  @Override
+  public String getVariableScopeKey() {
+    return variableScopeKey;
+  }
+
+  protected RuntimeException notYetImplemented() {
+    return new RuntimeException("Recording this method is not implemented");
+  }
+
+  protected RuntimeException cannotModifyState() {
+    return new RuntimeException("This event is read-only; cannot modify state");
+  }
+
+  @Override
+  public Map<String, Object> getVariables() {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public VariableMap getVariablesTyped() {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public VariableMap getVariablesTyped(boolean deserializeValues) {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public Map<String, Object> getVariablesLocal() {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public VariableMap getVariablesLocalTyped() {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public VariableMap getVariablesLocalTyped(boolean deserializeValues) {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public Object getVariable(String variableName) {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public Object getVariableLocal(String variableName) {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public <T extends TypedValue> T getVariableTyped(String variableName) {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public <T extends TypedValue> T getVariableTyped(String variableName, boolean deserializeValue) {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public <T extends TypedValue> T getVariableLocalTyped(String variableName) {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public <T extends TypedValue> T getVariableLocalTyped(String variableName, boolean deserializeValue) {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public Set<String> getVariableNames() {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public Set<String> getVariableNamesLocal() {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public void setVariable(String variableName, Object value) {
+    throw cannotModifyState();
+  }
+
+  @Override
+  public void setVariableLocal(String variableName, Object value) {
+    throw cannotModifyState();
+  }
+
+  @Override
+  public void setVariables(Map<String, ? extends Object> variables) {
+    throw cannotModifyState();
+  }
+
+  @Override
+  public void setVariablesLocal(Map<String, ? extends Object> variables) {
+    throw cannotModifyState();
+  }
+
+  @Override
+  public boolean hasVariables() {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public boolean hasVariablesLocal() {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public boolean hasVariable(String variableName) {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public boolean hasVariableLocal(String variableName) {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public void removeVariable(String variableName) {
+    throw cannotModifyState();
+  }
+
+  @Override
+  public void removeVariableLocal(String variableName) {
+    throw cannotModifyState();
+  }
+
+  @Override
+  public void removeVariables(Collection<String> variableNames) {
+    throw cannotModifyState();
+  }
+
+  @Override
+  public void removeVariablesLocal(Collection<String> variableNames) {
+    throw cannotModifyState();
+  }
+
+  @Override
+  public void removeVariables() {
+    throw cannotModifyState();
+  }
+
+  @Override
+  public void removeVariablesLocal() {
+    throw cannotModifyState();
+  }
+
+  @Override
+  public BpmnModelInstance getBpmnModelInstance() {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public FlowElement getBpmnModelElementInstance() {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public ProcessEngineServices getProcessEngineServices() {
+    throw notYetImplemented();
+  }
+
+  public String getActivityInstanceId() {
+    return activityInstanceId;
+  }
+
+  public String getCurrentActivityId() {
+    return currentActivityId;
+  }
+
+  public String getCurrentActivityName() {
+    return currentActivityName;
+  }
+
+  public String getCurrentTransitionId() {
+    return currentTransitionId;
+  }
+
+  public String getParentActivityInstanceId() {
+    return parentActivityInstanceId;
+  }
+
+  public String getParentId() {
+    return parentId;
+  }
+
+  public String getProcessBusinessKey() {
+    return processBusinessKey;
+  }
+
+  public String getProcessDefinitionId() {
+    return processDefinitionId;
+  }
+
+
+  public String getProcessInstanceId() {
+    return processInstanceId;
+  }
+
+  public String getTenantId() {
+    return tenantId;
+  }
+
+  @Override
+  public void setVariable(String variableName, Object value, String activityId) {
+    this.cannotModifyState();
+  }
+
+  @Override
+  public DelegateExecution getProcessInstance() {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public DelegateExecution getSuperExecution() {
+    throw notYetImplemented();
+  }
+
+  @Override
+  public boolean isCanceled() {
+    throw notYetImplemented();
+  }
+
+
+
+}
Index: engine/src/test/java/org/camunda/bpm/engine/test/bpmn/multiinstance/SubBean.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- engine/src/test/java/org/camunda/bpm/engine/test/bpmn/multiinstance/SubBean.java	(revision )
+++ engine/src/test/java/org/camunda/bpm/engine/test/bpmn/multiinstance/SubBean.java	(revision )
@@ -0,0 +1,32 @@
+/* Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.camunda.bpm.engine.test.bpmn.multiinstance;
+
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.camunda.bpm.engine.delegate.DelegateExecution;
+
+public class SubBean implements Serializable {
+
+  private static final long serialVersionUID = 1L;
+
+  protected static List<SubEvent> RECORDED_EVENTS = new ArrayList<SubEvent>();
+
+  public void doIt(DelegateExecution delegateExecution) {
+
+    SubEvent.recordEventFor(delegateExecution);
+  }
+}
Index: engine/src/main/java/org/camunda/bpm/engine/impl/bpmn/behavior/MultiInstanceActivityBehavior.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- engine/src/main/java/org/camunda/bpm/engine/impl/bpmn/behavior/MultiInstanceActivityBehavior.java	(revision 13396e10cc0801825458604bd2ee22f2799e5d48)
+++ engine/src/main/java/org/camunda/bpm/engine/impl/bpmn/behavior/MultiInstanceActivityBehavior.java	(revision )
@@ -15,6 +15,7 @@
 
 import static org.camunda.bpm.engine.impl.util.EnsureUtil.ensureNotNull;
 
+import java.io.Serializable;
 import java.util.Collection;
 import java.util.Iterator;
 
@@ -56,7 +57,10 @@
   protected String collectionVariable;
   protected String collectionElementVariable;
 
-  @Override
+  private Collection collectionExpressionValue;
+  private Collection collectionVariableValue;
+
+	@Override
   public void execute(ActivityExecution execution) throws Exception {
     int nrOfInstances = resolveNrOfInstances(execution);
     if (nrOfInstances == 0) {
@@ -82,9 +86,9 @@
     if (usesCollection() && collectionElementVariable != null) {
       Collection<?> collection = null;
       if (collectionExpression != null) {
-        collection = (Collection<?>) collectionExpression.getValue(execution);
+        collection = collectionExpressionValue;
       } else if (collectionVariable != null) {
-        collection = (Collection<?>) execution.getVariable(collectionVariable);
+        collection = collectionVariableValue;
       }
 
       Object value = getElementAtIndex(loopCounter, collection);
@@ -102,16 +106,18 @@
       nrOfInstances = resolveLoopCardinality(execution);
     } else if (collectionExpression != null) {
       Object obj = collectionExpression.getValue(execution);
-      if (!(obj instanceof Collection)) {
+      if (!(obj instanceof Collection) || !(obj instanceof Serializable)) {
         throw LOG.unresolvableExpressionException(collectionExpression.getExpressionText(), "Collection");
       }
-      nrOfInstances = ((Collection<?>) obj).size();
+      collectionExpressionValue = ((Collection<?>) obj);
+      nrOfInstances = collectionExpressionValue.size();
     } else if (collectionVariable != null) {
       Object obj = execution.getVariable(collectionVariable);
-      if (!(obj instanceof Collection)) {
+      if (!(obj instanceof Collection) || !(obj instanceof Serializable)) {
         throw LOG.invalidVariableTypeException(collectionVariable, "Collection");
       }
-      nrOfInstances = ((Collection<?>) obj).size();
+      collectionVariableValue = ((Collection<?>) obj);
+      nrOfInstances = collectionVariableValue.size();
     } else {
       throw LOG.resolveCollectionExpressionOrVariableReferenceException();
     }
Index: engine/src/test/resources/org/camunda/bpm/engine/test/bpmn/multiinstance/MultiInstanceTest.testSequentialSubProcessOnCollectionExpression.bpmn20.xml
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- engine/src/test/resources/org/camunda/bpm/engine/test/bpmn/multiinstance/MultiInstanceTest.testSequentialSubProcessOnCollectionExpression.bpmn20.xml	(revision )
+++ engine/src/test/resources/org/camunda/bpm/engine/test/bpmn/multiinstance/MultiInstanceTest.testSequentialSubProcessOnCollectionExpression.bpmn20.xml	(revision )
@@ -0,0 +1,42 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<definitions id="definition" 
+  xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL"
+  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xmlns:camunda="http://camunda.org/schema/1.0/bpmn"
+  targetNamespace="Examples">
+  
+  <process id="process" isExecutable="true">
+  
+    <startEvent id="theStart">
+        <outgoing>sub</outgoing>
+    </startEvent>
+
+    <subProcess id="sub" name="sub with seq multiinstance">
+        <incoming>sid-80FBB955-C0F8-43B2-84E9-9864C54E88D4</incoming>
+        <outgoing>sid-F12788B2-2E2A-46E8-9390-B1A058986EB2</outgoing>
+
+        <multiInstanceLoopCharacteristics isSequential="true" camunda:elementVariable="elementVar" camunda:collection="${myBean.resolveCollection(execution)}"/>
+        <serviceTask id="serviceTask_sub" implementation="webService" camunda:expression="#{mySubBean.doIt(execution)}">
+            <incoming>sub-start</incoming>
+            <outgoing>sub-end</outgoing>
+        </serviceTask>
+        <startEvent id="subStart">
+            <outgoing>serviceTask_sub</outgoing>
+        </startEvent>
+        <endEvent id="subEnd">
+            <incoming>serviceTask_sub</incoming>
+        </endEvent>
+        <sequenceFlow id="sub_flow_start" sourceRef="subStart" targetRef="serviceTask_sub" />
+        <sequenceFlow id="sub_flow_end" sourceRef="serviceTask_sub" targetRef="subEnd" />
+    </subProcess>
+
+      <sequenceFlow id="sid-80FBB955-C0F8-43B2-84E9-9864C54E88D4" name="" sourceRef="theStart" targetRef="sub" />
+      <sequenceFlow id="sid-F12788B2-2E2A-46E8-9390-B1A058986EB2" name="" sourceRef="sub" targetRef="theEnd" />
+
+      <endEvent id="theEnd">
+        <incoming>sub</incoming>
+    </endEvent>
+    
+  </process>
+
+</definitions>
\ No newline at end of file
Index: engine/src/test/java/org/camunda/bpm/engine/test/bpmn/multiinstance/MultiInstanceTest.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- engine/src/test/java/org/camunda/bpm/engine/test/bpmn/multiinstance/MultiInstanceTest.java	(revision 13396e10cc0801825458604bd2ee22f2799e5d48)
+++ engine/src/test/java/org/camunda/bpm/engine/test/bpmn/multiinstance/MultiInstanceTest.java	(revision )
@@ -397,19 +397,33 @@
   }
 
   @Deployment
-  public void FAILING_testParallelUserTasksBasedOnCollectionExpression() {
+  public void testParallelUserTasksBasedOnCollectionExpression() {
     DelegateEvent.clearEvents();
 
-    runtimeService.startProcessInstanceByKey("process",
-        Variables.createVariables().putValue("myBean", new DelegateBean()));
+    runtimeService.startProcessInstanceByKey("process", Variables.createVariables().putValue("myBean", new DelegateBean()));
 
     List<DelegateEvent> recordedEvents = DelegateEvent.getEvents();
-    assertEquals(2, recordedEvents.size());
 
+    assertEquals(1, recordedEvents.size());
     assertEquals("miTasks#multiInstanceBody", recordedEvents.get(0).getCurrentActivityId());
-    assertEquals("miTasks#multiInstanceBody", recordedEvents.get(1).getCurrentActivityId()); // or miTasks
 
     DelegateEvent.clearEvents();
+  }
+
+  @Deployment
+  public void testSequentialSubProcessOnCollectionExpression() {
+    DelegateEvent.clearEvents();
+    SubEvent.clearEvents();
+
+    runtimeService.startProcessInstanceByKey("process", Variables.createVariables().putValue("myBean", new DelegateBean()).putValue("mySubBean", new SubBean()));
+
+	assertEquals(3, SubEvent.getEvents().size());
+    List<DelegateEvent> delegateEvents = DelegateEvent.getEvents();
+    assertEquals(1, delegateEvents.size());
+    assertEquals("sub#multiInstanceBody", delegateEvents.get(0).getCurrentActivityId());
+
+	SubEvent.clearEvents();
+	DelegateEvent.clearEvents();
   }
 
   @Deployment