diff --git a/libcxx/include/__string b/libcxx/include/__string
--- a/libcxx/include/__string
+++ b/libcxx/include/__string
@@ -563,11 +563,8 @@
 _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR
 inline size_t __char_traits_length_checked(const typename _Traits::char_type* __s) _NOEXCEPT {
-#if _LIBCPP_DEBUG_LEVEL >= 1
-  return __s ? _Traits::length(__s) : (_VSTD::__libcpp_debug_function(_VSTD::__libcpp_debug_info(__FILE__, __LINE__, "p == nullptr", "null pointer pass to non-null argument of char_traits<...>::length")), 0);
-#else
+  _LIBCPP_ASSERT(__s != nullptr, "null pointer passed to non-null argument of char_traits<...>::length");
   return _Traits::length(__s);
-#endif
 }
 
 #ifndef _LIBCPP_HAS_NO_CHAR8_T