diff --git a/mozilla/xpinstall/src/nsXPInstallManager.cpp b/mozilla/xpinstall/src/nsXPInstallManager.cpp
index b8e63e589bc..32f23a902a5 100644
--- a/mozilla/xpinstall/src/nsXPInstallManager.cpp
+++ b/mozilla/xpinstall/src/nsXPInstallManager.cpp
@@ -794,6 +794,8 @@ nsXPInstallManager::OnDataAvailable(nsIChannel* channel, nsISupports *ctxt,
     {
         // returning an error will stop the download. We may get extra
         // OnData calls if they were already queued so beware
+        if (mDlg)
+            mDlg->Close();
         return NS_ERROR_FAILURE;
     }