diff --git a/util/ng_corpus_generator.cpp b/util/ng_corpus_generator.cpp
index 68aa5583..c18f2398 100644
--- a/util/ng_corpus_generator.cpp
+++ b/util/ng_corpus_generator.cpp
@@ -221,7 +221,7 @@ class CorpusGeneratorImpl : public CorpusGenerator {
 public:
     CorpusGeneratorImpl(const NGHolder &graph_in, const ExpressionInfo &expr_in,
                         CorpusProperties &props);
-    ~CorpusGeneratorImpl() = default;
+    virtual ~CorpusGeneratorImpl() = default;
 
     void generateCorpus(vector<string> &data) override;