diff --git a/src/cxon/lang/common/cio/class.hxx b/src/cxon/lang/common/cio/class.hxx
index ee9a1cfd..eaa1cc62 100644
--- a/src/cxon/lang/common/cio/class.hxx
+++ b/src/cxon/lang/common/cio/class.hxx
@@ -88,7 +88,7 @@ namespace cxon { namespace cio { namespace cls { // bare object support structur
 #if __cplusplus < 202002L // use of function template name with no prior declaration in function call with explicit template arguments is a C++20 extension [-Wc++20-extensions]
     namespace cxon {
         template <typename X, typename T, typename II, typename Cx> // read_field in cxon namespace
-            inline auto read_field(T& t, const char* name, std::size_t nale, II& i, II e, Cx& cx);
+            inline bool read_field(T& t, const char* name, std::size_t nale, II& i, II e, Cx& cx);
     }
 #endif