--- a/content/base/src/nsObjectLoadingContent.cpp
+++ b/content/base/src/nsObjectLoadingContent.cpp
@@ -348,17 +348,18 @@ nsObjectLoadingContent::~nsObjectLoading
   DestroyImageLoadingContent();
   if (mFrameLoader) {
     mFrameLoader->Destroy();
   }
 }
 
 // nsIRequestObserver
 NS_IMETHODIMP
-nsObjectLoadingContent::OnStartRequest(nsIRequest *aRequest, nsISupports *aContext)
+nsObjectLoadingContent::OnStartRequest(nsIRequest *aRequest,
+                                       nsISupports *aContext)
 {
   if (aRequest != mChannel) {
     // This is a bit of an edge case - happens when a new load starts before the
     // previous one got here
     return NS_BINDING_ABORTED;
   }
 
   // We're done with the classifier
@@ -404,16 +405,27 @@ nsObjectLoadingContent::OnStartRequest(n
     // end up trying to dispatch to a nsFrameLoader, which will complain that
     // it couldn't find a way to handle application/octet-stream
 
     chan->SetContentType(mContentType);
   } else {
     mContentType = channelType;
   }
 
+  nsCOMPtr<nsIURI> uri;
+  chan->GetURI(getter_AddRefs(uri));
+
+  if (mContentType.EqualsASCII(APPLICATION_OCTET_STREAM)) {
+    nsCAutoString extType;
+    if (IsPluginEnabledByExtension(uri, extType)) {
+      mContentType = extType;
+      chan->SetContentType(extType);
+    }
+  }
+
   // Now find out what type the content is
   // UnloadContent will set our type to null; need to be sure to only set it to
   // the real value on success
   ObjectType newType = GetTypeOfContent(mContentType);
   LOG(("OBJLC [%p]: OnStartRequest: Content Type=<%s> Old type=%u New Type=%u\n",
        this, mContentType.get(), mType, newType));
 
   // Now do a content policy check
@@ -425,18 +437,16 @@ nsObjectLoadingContent::OnStartRequest(n
       break;
     case eType_Document:
       contentPolicyType = nsIContentPolicy::TYPE_SUBDOCUMENT;
       break;
     default:
       contentPolicyType = nsIContentPolicy::TYPE_OBJECT;
       break;
   }
-  nsCOMPtr<nsIURI> uri;
-  chan->GetURI(getter_AddRefs(uri));
   nsCOMPtr<nsIContent> thisContent = 
     do_QueryInterface(static_cast<nsIImageLoadingContent*>(this));
   NS_ASSERTION(thisContent, "must be a content");
 
   nsIDocument* doc = thisContent->GetOwnerDoc();
   if (!doc) {
     Fallback(PR_FALSE);
     return NS_BINDING_ABORTED;