diff --git a/impl/src/main/java/com/sun/faces/lifecycle/ClientWindowImpl.java b/impl/src/main/java/com/sun/faces/lifecycle/ClientWindowImpl.java
index 5f1cabd651..b0d3cc3017 100644
--- a/impl/src/main/java/com/sun/faces/lifecycle/ClientWindowImpl.java
+++ b/impl/src/main/java/com/sun/faces/lifecycle/ClientWindowImpl.java
@@ -16,6 +16,7 @@
 
 package com.sun.faces.lifecycle;
 
+import static com.sun.faces.context.SessionMap.getMutex;
 import static com.sun.faces.renderkit.RenderKitUtils.PredefinedPostbackParameter.CLIENT_WINDOW_PARAM;
 
 import java.util.Map;
@@ -55,7 +56,7 @@ public void decode(FacesContext context) {
     }
 
     private String calculateClientWindow(FacesContext context) {
-        synchronized (context.getExternalContext().getSession(true)) {
+        synchronized (getMutex(context.getExternalContext().getSession(true))) {
             final String clientWindowCounterKey = "com.sun.faces.lifecycle.ClientWindowCounterKey";
             ExternalContext extContext = context.getExternalContext();
             Map<String, Object> sessionAttrs = extContext.getSessionMap();
diff --git a/impl/src/main/java/com/sun/faces/renderkit/ServerSideStateHelper.java b/impl/src/main/java/com/sun/faces/renderkit/ServerSideStateHelper.java
index 2dc7a67719..5c96f298aa 100644
--- a/impl/src/main/java/com/sun/faces/renderkit/ServerSideStateHelper.java
+++ b/impl/src/main/java/com/sun/faces/renderkit/ServerSideStateHelper.java
@@ -263,7 +263,7 @@ public Object getState(FacesContext ctx, String viewId) {
         }
 
         // noinspection SynchronizationOnLocalVariableOrMethodParameter
-        synchronized (sessionObj) {
+        synchronized (getMutex(sessionObj)) {
             Map logicalMap = (Map) externalCtx.getSessionMap().get(LOGICAL_VIEW_MAP);
             if (logicalMap != null) {
                 Map actualMap = (Map) logicalMap.get(idInLogicalMap);