diff --git a/headers/private/media/DecoderPlugin.h b/headers/private/media/DecoderPlugin.h
index 21804bb2af..b94d47efc6 100644
--- a/headers/private/media/DecoderPlugin.h
+++ b/headers/private/media/DecoderPlugin.h
@@ -40,7 +40,7 @@ private:
 };
 
 
-class DecoderPlugin : public MediaPlugin
+class DecoderPlugin : public virtual MediaPlugin
 {
 public:
 						DecoderPlugin();
diff --git a/headers/private/media/ReaderPlugin.h b/headers/private/media/ReaderPlugin.h
index 2fe640736d..bd81a4f912 100644
--- a/headers/private/media/ReaderPlugin.h
+++ b/headers/private/media/ReaderPlugin.h
@@ -47,7 +47,7 @@ public: // XXX for test programs only
 };
 
 
-class ReaderPlugin : public MediaPlugin
+class ReaderPlugin : public virtual MediaPlugin
 {
 public:
 	virtual Reader *NewReader() = 0;