diff --git a/dom/public/nsIScriptContext.h b/dom/public/nsIScriptContext.h
index 2dac1098a79c..d3bdaf670a2c 100644
--- a/dom/public/nsIScriptContext.h
+++ b/dom/public/nsIScriptContext.h
@@ -54,7 +54,6 @@ class nsIVariant;
 class nsIObjectInputStream;
 class nsIObjectOutputStream;
 class nsScriptObjectHolder;
-class nsIDOMDocument;
 
 typedef void (*nsScriptTerminationFunc)(nsISupports* aRef);
 
@@ -443,9 +442,10 @@ public:
 
   /**
    * Tell the context our global has a new document, and the scope
-   * used by it.
+   * used by it.  Use nsISupports to avoid dependency issues - but expect
+   * a QI for nsIDOMDocument and/or nsIDocument.
    */
-  virtual void DidSetDocument(nsIDOMDocument *aDoc, void *aGlobal) = 0;
+  virtual void DidSetDocument(nsISupports *aDoc, void *aGlobal) = 0;
 
   /* Memory managment for script objects.  Used by the implementation of
    * nsScriptObjectHolder to manage the lifetimes of the held script objects.
diff --git a/dom/src/base/nsJSEnvironment.h b/dom/src/base/nsJSEnvironment.h
index 1f47bbf3c7e9..286db165c6c7 100644
--- a/dom/src/base/nsJSEnvironment.h
+++ b/dom/src/base/nsJSEnvironment.h
@@ -154,7 +154,7 @@ public:
 
   virtual void WillInitializeContext();
   virtual void DidInitializeContext();
-  virtual void DidSetDocument(nsIDOMDocument *aDocdoc, void *aGlobal) {;}
+  virtual void DidSetDocument(nsISupports *aDocdoc, void *aGlobal) {;}
 
   virtual nsresult Serialize(nsIObjectOutputStream* aStream, void *aScriptObject);
   virtual nsresult Deserialize(nsIObjectInputStream* aStream,
diff --git a/extensions/python/dom/src/nsPyContext.cpp b/extensions/python/dom/src/nsPyContext.cpp
index a8cf27302daf..36b9ea76de40 100644
--- a/extensions/python/dom/src/nsPyContext.cpp
+++ b/extensions/python/dom/src/nsPyContext.cpp
@@ -288,7 +288,7 @@ nsPythonContext::InitContext(nsIScriptGlobalObject *aGlobalObject)
 }
 
 void
-nsPythonContext::DidSetDocument(nsIDOMDocument *aDoc, void *aGlobal)
+nsPythonContext::DidSetDocument(nsISupports *aSupDoc, void *aGlobal)
 {
   NS_TIMELINE_MARK_FUNCTION("nsPythonContext::DidSetDocument");
   NS_ASSERTION(mDelegate != NULL, "No delegate");
@@ -298,9 +298,12 @@ nsPythonContext::DidSetDocument(nsIDOMDocument *aDoc, void *aGlobal)
 
   CEnterLeavePython _celp;
   PyObject *obDoc;
-  if (aDoc) {
-    obDoc = PyObject_FromNSDOMInterface(mDelegate, aDoc,
-                                        NS_GET_IID(nsIDOMDocument));
+  if (aSupDoc) {
+    nsCOMPtr<nsIDOMDocument> doc(do_QueryInterface(aSupDoc));
+    NS_ASSERTION(nsnull != doc, "not an nsIDOMDocument!?");
+    if (nsnull != doc)
+      obDoc = PyObject_FromNSDOMInterface(mDelegate, aSupDoc,
+                                          NS_GET_IID(nsIDOMDocument));
     if (!obDoc) {
       HandlePythonError();
       return;
diff --git a/extensions/python/dom/src/nsPyContext.h b/extensions/python/dom/src/nsPyContext.h
index e1950343f3f3..48cc75e4bdd9 100644
--- a/extensions/python/dom/src/nsPyContext.h
+++ b/extensions/python/dom/src/nsPyContext.h
@@ -204,7 +204,7 @@ public:
 
   virtual void WillInitializeContext();
   virtual void DidInitializeContext();
-  virtual void DidSetDocument(nsIDOMDocument *aDocdoc, void *aGlobal);
+  virtual void DidSetDocument(nsISupports *aDocdoc, void *aGlobal);
 
   virtual nsresult Serialize(nsIObjectOutputStream* aStream, void *aScriptObject);
   virtual nsresult Deserialize(nsIObjectInputStream* aStream,