diff --git a/pcm.hh b/pcm.hh
index e015430..d7b950e 100644
--- a/pcm.hh
+++ b/pcm.hh
@@ -17,6 +17,7 @@ struct WritePCM
 	virtual void silence(int) = 0;
 	virtual int rate() = 0;
 	virtual int channels() = 0;
+	virtual ~WritePCM() = default;
 };
 
 template <typename TYPE>
@@ -28,6 +29,7 @@ struct ReadPCM
 	virtual int rate() = 0;
 	virtual int channels() = 0;
 	virtual int frames() { return -1; }
+	virtual ~ReadPCM() = default;
 };
 
 }
diff --git a/window.hh b/window.hh
index 8e685e6..a3c7e5c 100644
--- a/window.hh
+++ b/window.hh
@@ -16,6 +16,7 @@ template <typename TYPE>
 struct WinFunc
 {
 	virtual TYPE operator () (int, int) = 0;
+	virtual ~WinFunc() = default;
 };
 
 template <int TAPS, typename TYPE>