diff --git a/mailnews/base/src/nsMessenger.cpp b/mailnews/base/src/nsMessenger.cpp
index 953b462b6a..c9de533ae7 100644
--- a/mailnews/base/src/nsMessenger.cpp
+++ b/mailnews/base/src/nsMessenger.cpp
@@ -233,6 +233,13 @@ NS_IMETHODIMP nsMessenger::SetWindow(mozIDOMWindowProxy *aWin, nsIMsgWindow *aMs
     do_GetService(NS_MSGMAILSESSION_CONTRACTID, &rv);
   NS_ENSURE_SUCCESS(rv, rv);
 
+  // Remove the folder listener if we added it, i.e. if mWindow is non-null
+  if (mWindow)
+  {
+    rv = mailSession->RemoveFolderListener(this);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
   if (aWin)
   {
     mMsgWindow = aMsgWindow;
@@ -271,13 +278,6 @@ NS_IMETHODIMP nsMessenger::SetWindow(mozIDOMWindowProxy *aWin, nsIMsgWindow *aMs
   } // if aWin
   else
   {
-    // Remove the folder listener if we added it, i.e. if mWindow is non-null
-    if (mWindow)
-    {
-      rv = mailSession->RemoveFolderListener(this);
-      NS_ENSURE_SUCCESS(rv, rv);
-    }
-
     mWindow = nullptr;
   }
 
diff --git a/mailnews/imap/src/nsImapMailFolder.cpp b/mailnews/imap/src/nsImapMailFolder.cpp
index da1411cd08..1d08472bb9 100644
--- a/mailnews/imap/src/nsImapMailFolder.cpp
+++ b/mailnews/imap/src/nsImapMailFolder.cpp
@@ -1803,6 +1803,7 @@ nsImapMailFolder::GetImapIncomingServer(nsIImapIncomingServer **aImapIncomingSer
   if (NS_SUCCEEDED(GetServer(getter_AddRefs(server))) && server)
   {
     nsCOMPtr <nsIImapIncomingServer> incomingServer = do_QueryInterface(server);
+    NS_ENSURE_TRUE(incomingServer, NS_ERROR_NO_INTERFACE);
     incomingServer.swap(*aImapIncomingServer);
     return NS_OK;
   }