diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index 5623cbcaa93..0b2a4ce3520 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -1194,6 +1194,18 @@ JS_SetContextPrivate(JSContext *cx, void *data)
     cx->data = data;
 }
 
+JS_PUBLIC_API(void *)
+JS_GetSecondContextPrivate(JSContext *cx)
+{
+    return cx->data2;
+}
+
+JS_PUBLIC_API(void)
+JS_SetSecondContextPrivate(JSContext *cx, void *data)
+{
+    cx->data2 = data;
+}
+
 JS_PUBLIC_API(JSRuntime *)
 JS_GetRuntime(JSContext *cx)
 {
diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 68d9cac0a18..a982ae6f8ef 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -2085,6 +2085,12 @@ JS_GetContextPrivate(JSContext *cx);
 extern JS_PUBLIC_API(void)
 JS_SetContextPrivate(JSContext *cx, void *data);
 
+extern JS_PUBLIC_API(void *)
+JS_GetSecondContextPrivate(JSContext *cx);
+
+extern JS_PUBLIC_API(void)
+JS_SetSecondContextPrivate(JSContext *cx, void *data);
+
 extern JS_PUBLIC_API(JSRuntime *)
 JS_GetRuntime(JSContext *cx);
 
diff --git a/js/xpconnect/src/XPCContext.cpp b/js/xpconnect/src/XPCContext.cpp
index ea48216abe8..15c35521191 100644
--- a/js/xpconnect/src/XPCContext.cpp
+++ b/js/xpconnect/src/XPCContext.cpp
@@ -42,6 +42,8 @@
 
 #include "xpcprivate.h"
 
+#include "jsapi.h"
+
 /***************************************************************************/
 
 XPCContext::XPCContext(XPCJSRuntime* aRuntime,
@@ -59,15 +61,15 @@ XPCContext::XPCContext(XPCJSRuntime* aRuntime,
 
     PR_INIT_CLIST(&mScopes);
 
-    NS_ASSERTION(!mJSContext->data2, "Must be null");
-    mJSContext->data2 = this;
+    NS_ASSERTION(!JS_GetSecondContextPrivate(mJSContext), "Must be null");
+    JS_SetSecondContextPrivate(mJSContext, this);
 }
 
 XPCContext::~XPCContext()
 {
     MOZ_COUNT_DTOR(XPCContext);
-    NS_ASSERTION(mJSContext->data2 == this, "Must match this");
-    mJSContext->data2 = nsnull;
+    NS_ASSERTION(JS_GetSecondContextPrivate(mJSContext) == this, "Must match this");
+    JS_SetSecondContextPrivate(mJSContext, nsnull);
     NS_IF_RELEASE(mException);
     NS_IF_RELEASE(mSecurityManager);
 
diff --git a/js/xpconnect/src/xpcprivate.h b/js/xpconnect/src/xpcprivate.h
index ff7769f3a2c..2542fec62fc 100644
--- a/js/xpconnect/src/xpcprivate.h
+++ b/js/xpconnect/src/xpcprivate.h
@@ -859,8 +859,8 @@ class XPCContext
 public:
     static XPCContext* GetXPCContext(JSContext* aJSContext)
         {
-            NS_ASSERTION(aJSContext->data2, "should already have XPCContext");
-            return static_cast<XPCContext *>(aJSContext->data2);
+            NS_ASSERTION(JS_GetSecondContextPrivate(aJSContext), "should already have XPCContext");
+            return static_cast<XPCContext *>(JS_GetSecondContextPrivate(aJSContext));
         }
 
     XPCJSRuntime* GetRuntime() const {return mRuntime;}