diff --git a/src/calibre/utils/cpp_binding.h b/src/calibre/utils/cpp_binding.h
index 2f1375b24f..abaa94fe9e 100644
--- a/src/calibre/utils/cpp_binding.h
+++ b/src/calibre/utils/cpp_binding.h
@@ -44,6 +44,7 @@ class generic_raii {
 class wchar_raii : public generic_raii<wchar_t*, PyMem_Free> {
 	public:
 		explicit wchar_raii() noexcept {}
+		explicit wchar_raii(wchar_t *h) noexcept {}
 		explicit wchar_raii(PyObject *unicode_object) noexcept {
 			if (!unicode_object || !PyUnicode_Check(unicode_object)) { PyErr_SetString(PyExc_TypeError, "Not a unicode object"); return; }
 			handle = PyUnicode_AsWideCharString(unicode_object, NULL);