diff --git a/scheduler/interval-generator.h b/scheduler/interval-generator.h
index ce95b5a..027e6ab 100644
--- a/scheduler/interval-generator.h
+++ b/scheduler/interval-generator.h
@@ -32,6 +32,8 @@
 class IntervalGenerator
 {
 public:
+  virtual ~IntervalGenerator () { }
+  
   virtual double
   nextInterval() = 0;
 };