diff --git a/include/pybind11/descr.h b/include/pybind11/descr.h
index 0104e2b..4123cc1 100644
--- a/include/pybind11/descr.h
+++ b/include/pybind11/descr.h
@@ -93,7 +93,7 @@
     return _(text2);
 }
 
-template <size_t Size> auto constexpr _() {
+template <size_t Size> auto constexpr _() -> decltype(int_to_str<Size / 10, Size % 10>::digits) {
     return int_to_str<Size / 10, Size % 10>::digits;
 }