diff --git a/Source/cmIfCommand.h b/Source/cmIfCommand.h
index 2523f8ba3..1c9bef3ef 100644
--- a/Source/cmIfCommand.h
+++ b/Source/cmIfCommand.h
@@ -28,6 +28,7 @@
 class cmIfFunctionBlocker : public cmFunctionBlocker
 {
 public:
+  virtual ~cmIfFunctionBlocker() {}
   virtual bool IsFunctionBlocked(const char *name, const std::vector<std::string> &args, 
                                  const cmMakefile &mf) const;
   virtual bool ShouldRemove(const char *name, const std::vector<std::string> &args,