diff --git a/libcxx/include/__format/format_context.h b/libcxx/include/__format/format_context.h
--- a/libcxx/include/__format/format_context.h
+++ b/libcxx/include/__format/format_context.h
@@ -98,7 +98,7 @@
   basic_format_context& operator=(const basic_format_context&) = delete;
 
   _LIBCPP_HIDE_FROM_ABI basic_format_arg<basic_format_context>
-  arg(size_t __id) const {
+  arg(size_t __id) const noexcept {
     return __args_.get(__id);
   }
 #ifndef _LIBCPP_HAS_NO_LOCALIZATION
diff --git a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/arg.pass.cpp b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/arg.pass.cpp
--- a/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/arg.pass.cpp
+++ b/libcxx/test/std/utilities/format/format.formatter/format.context/format.context/arg.pass.cpp
@@ -34,6 +34,7 @@
   const std::basic_format_context context =
       test_format_context_create(OutIt{output}, args);
   LIBCPP_ASSERT(args.__size() == 4);
+  ASSERT_NOEXCEPT(context.arg(0));
   for (size_t i = 0, e = args.__size(); i != e; ++i) {
     assert(context.arg(i));
   }