diff --git a/src/security/transform/strip-space.hpp b/src/security/transform/strip-space.hpp
index 7cc4dc8..d0e50aa 100644
--- a/src/security/transform/strip-space.hpp
+++ b/src/security/transform/strip-space.hpp
@@ -44,7 +44,7 @@
   StripSpace(const char* whitespaces = DEFAULT_WHITESPACES);
 
 private:
-  virtual size_t
+  size_t
   convert(const uint8_t* buf, size_t buflen) final;
 
 private: