diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b38d22835..956f376dd 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -402,7 +402,8 @@ jobs:
                             -DCMAKE_CXX_STANDARD=11 \
                             -DPYTHON_EXECUTABLE=$(python3 -c "import sys; print(sys.executable)") \
                             -DCMAKE_CXX_FLAGS="-Wc,--pending_instantiations=0" \
-                            -DPYBIND11_TEST_FILTER="test_smart_ptr.cpp;test_virtual_functions.cpp"
+                            -DPYBIND11_TEST_FILTER="test_smart_ptr.cpp;test_virtual_functions.cpp" \
+                            -DCMAKE_BUILD_TYPE=Release
 
     # Building before installing Pip should produce a warning but not an error
     - name: Build
diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h
index 8678d7003..ab6cc3473 100644
--- a/include/pybind11/pytypes.h
+++ b/include/pybind11/pytypes.h
@@ -449,7 +449,7 @@ public:
 
 private:
     mutable std::string m_lazy_what;
-    object m_type, m_value, m_trace;
+    mutable object m_type, m_value, m_trace;
 };
 #if defined(_MSC_VER)
 #    pragma warning(pop)