diff --git a/src/algs/ags/solver.cc b/src/algs/ags/solver.cc
index 63b8760..b837112 100644
--- a/src/algs/ags/solver.cc
+++ b/src/algs/ags/solver.cc
@@ -38,6 +38,8 @@ namespace
         mRightBound = rightBound;
       }
 
+      virtual ~ProblemInternal() {}
+
       double Calculate(const double* y, int fNumber) const
       {
         return mFunctions[fNumber](y);