diff --git a/mozilla/netwerk/streamconv/converters/nsMultiMixedConv.h b/mozilla/netwerk/streamconv/converters/nsMultiMixedConv.h
index 5cc10eef429..fb6889f2325 100644
--- a/mozilla/netwerk/streamconv/converters/nsMultiMixedConv.h
+++ b/mozilla/netwerk/streamconv/converters/nsMultiMixedConv.h
@@ -38,7 +38,7 @@ public:
 
     // nsMultiMixedConv methods
     nsMultiMixedConv();
-    ~nsMultiMixedConv();
+    virtual ~nsMultiMixedConv();
     nsresult Init();
     nsresult SendPart(const char *aBuffer, nsIChannel *aChannel, nsISupports *aCtxt);