diff --git a/tests/limited-io.hpp b/tests/limited-io.hpp
index 3e4be61..437335c 100644
--- a/tests/limited-io.hpp
+++ b/tests/limited-io.hpp
@@ -87,7 +87,7 @@
 private:
   /** \brief an exception to stop IO operation
    */
-  class StopException
+  class StopException : public std::exception
   {
   };