diff --git a/subprocess.hpp b/subprocess.hpp
index 1d6fdb8..b22a00a 100755
--- a/subprocess.hpp
+++ b/subprocess.hpp
@@ -618,6 +618,7 @@ public:
 private:
   struct HolderBase {
     virtual void operator()() const = 0;
+    virtual ~HolderBase(){};
   };
   template <typename T>
   struct FuncHolder: HolderBase {