diff --git a/mozilla/modules/plugin/samples/simple/npsimple.cpp b/mozilla/modules/plugin/samples/simple/npsimple.cpp
index 9f27ea1164e..1fcc08e1742 100644
--- a/mozilla/modules/plugin/samples/simple/npsimple.cpp
+++ b/mozilla/modules/plugin/samples/simple/npsimple.cpp
@@ -964,6 +964,11 @@ NS_METHOD
 SimplePluginStreamListener::OnDataAvailable(const char* url, nsIPluginInputStream* input,
                                             PRUint32 offset, PRUint32 length)
 {
+    if (strcmp(url, "http://warp/java/oji/") == 0 && offset != 0) {
+        // Try closing the stream prematurely
+        input->Close();
+        return NS_OK;
+    }
     char* buffer = new char[length];
     if (buffer) {
         PRInt32 amountRead = 0;
diff --git a/mozilla/modules/plugin/src/npglue.cpp b/mozilla/modules/plugin/src/npglue.cpp
index c259447da36..f4256200c96 100644
--- a/mozilla/modules/plugin/src/npglue.cpp
+++ b/mozilla/modules/plugin/src/npglue.cpp
@@ -503,6 +503,12 @@ NPL_WriteReady(NET_StreamClass *stream)
             ret = userStream->WriteReady();
 #else
             ret = NP_MAXREADY;
+#ifdef NEW_PLUGIN_STREAM_API
+            nsPluginInputStream* inStr = (nsPluginInputStream*)newstream->pstream->pdata;
+            if (inStr->IsClosed()) {
+                ret = -1;
+            }
+#endif
 #endif
         }
         else if (ISFUNCPTR(newstream->handle->f->writeready)) {
@@ -582,12 +588,18 @@ NPL_Write(NET_StreamClass *stream, const unsigned char *str, int32 len)
 #ifdef NEW_PLUGIN_STREAM_API
 
         nsPluginInputStream* inStr = (nsPluginInputStream*)newstream->pstream->pdata;
-        nsIPluginStreamListener* listener = inStr->GetListener();
-        nsresult err = inStr->ReceiveData((const char*)str, urls->position, len);
-        if (err == NS_OK) {
-            err = listener->OnDataAvailable((const char*)urls->address, inStr, urls->position, len);
+        if (inStr->IsClosed()) {
+            ret = -1;
+        }
+        else {
+            nsIPluginStreamListener* listener = inStr->GetListener();
+            nsresult err = inStr->ReceiveData((const char*)str, urls->position, len);
+            if (err == NS_OK) {
+                err = listener->OnDataAvailable((const char*)urls->address, inStr, urls->position, len);
+            }
+            if (err != NS_OK)
+                ret = -1;
         }
-        PR_ASSERT(err == NS_OK);        // XXX this error should go somewhere
 
 #else // !NEW_PLUGIN_STREAM_API
 
diff --git a/mozilla/modules/plugin/src/npglue.h b/mozilla/modules/plugin/src/npglue.h
index 7619f89734e..5a2c064ab06 100644
--- a/mozilla/modules/plugin/src/npglue.h
+++ b/mozilla/modules/plugin/src/npglue.h
@@ -774,6 +774,7 @@ public:
 
     nsIPluginStreamListener* GetListener(void) { return mListener; }
     nsPluginStreamType GetStreamType(void) { return mStreamType; }
+    PRBool IsClosed(void) { return mClosed; }
 
     void SetStreamInfo(URL_Struct* urls, np_stream* stream) {
         mUrls = urls;
@@ -797,6 +798,7 @@ protected:
     };
 
     BufferElement* mBuffer;
+    PRBool mClosed;
 //    PRUint32 mReadCursor;
 
 //    PRUint32 mBufferLength;
diff --git a/mozilla/modules/plugin/src/nsplugin.cpp b/mozilla/modules/plugin/src/nsplugin.cpp
index 8bcc88c2c60..e581c04ad1e 100644
--- a/mozilla/modules/plugin/src/nsplugin.cpp
+++ b/mozilla/modules/plugin/src/nsplugin.cpp
@@ -1640,7 +1640,7 @@ nsPluginInputStream::nsPluginInputStream(nsIPluginStreamListener* listener,
                                          nsPluginStreamType streamType)
     : mListener(listener), mStreamType(streamType),
       mUrls(NULL), mStream(NULL),
-      mBuffer(NULL)
+      mBuffer(NULL), mClosed(PR_FALSE)
 //      mBuffer(NULL), mBufferLength(0), mAmountRead(0)
 {
     NS_INIT_REFCNT();
@@ -1686,14 +1686,21 @@ nsPluginInputStream::Cleanup(void)
         }
         mBuffer = NULL;
     }
+    mClosed = PR_TRUE;
 }
 
 NS_METHOD
 nsPluginInputStream::Close(void)
 {
+    NPError err = NPERR_NO_ERROR;
     Cleanup();
-    NPError err = npn_destroystream(mStream->instance->npp, mStream->pstream, 
-                                    nsPluginReason_UserBreak);
+#if 0   /* According to the plugin documentation, this would seem to be the 
+         * right thing to do here, but it's not (and calling NPN_DestroyStream
+         * in the 4.0 browser during an NPP_Write call will crash the browser).
+         */
+    err = npn_destroystream(mStream->instance->npp, mStream->pstream, 
+                            nsPluginReason_UserBreak);
+#endif
     return fromNPError[err];
 }
 
diff --git a/mozilla/modules/plugin/test/npsimple.cpp b/mozilla/modules/plugin/test/npsimple.cpp
index 9f27ea1164e..1fcc08e1742 100644
--- a/mozilla/modules/plugin/test/npsimple.cpp
+++ b/mozilla/modules/plugin/test/npsimple.cpp
@@ -964,6 +964,11 @@ NS_METHOD
 SimplePluginStreamListener::OnDataAvailable(const char* url, nsIPluginInputStream* input,
                                             PRUint32 offset, PRUint32 length)
 {
+    if (strcmp(url, "http://warp/java/oji/") == 0 && offset != 0) {
+        // Try closing the stream prematurely
+        input->Close();
+        return NS_OK;
+    }
     char* buffer = new char[length];
     if (buffer) {
         PRInt32 amountRead = 0;