diff --git a/libcxx/include/__locale b/libcxx/include/__locale
index d1d66f94d0d7..0a275c07a9ab 100644
--- a/libcxx/include/__locale
+++ b/libcxx/include/__locale
@@ -1229,8 +1229,6 @@ _LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS codecvt_byname<w
 _LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS codecvt_byname<char16_t, char, mbstate_t>)
 _LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS codecvt_byname<char32_t, char, mbstate_t>)
 
-_LIBCPP_NORETURN _LIBCPP_FUNC_VIS void __throw_runtime_error(const char*);
-
 template <size_t _Np>
 struct __narrow_to_utf8
 {