diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 912c4a3cb..847a7b34a 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -498,7 +498,7 @@ public:
     const object &trace() const { return m_trace; }
 
 private:
-    mutable object m_type, m_value, m_trace;
+    object m_type, m_value, m_trace;
     mutable std::string m_lazy_what;
 };
 #if defined(_MSC_VER)