diff --git a/libcxx/test/libcxx/type_traits/is_scalar.objc.pass.mm b/libcxx/test/libcxx/type_traits/is_scalar.objc.pass.mm
--- a/libcxx/test/libcxx/type_traits/is_scalar.objc.pass.mm
+++ b/libcxx/test/libcxx/type_traits/is_scalar.objc.pass.mm
@@ -17,7 +17,9 @@
 // Make sure we report that blocks are scalar types.
 
 #include <type_traits>
+#if __cplusplus >= 201703L
 #include <optional>
+#endif // C++17
 
 struct Foo { };
 template <int> struct Arg { };
@@ -35,6 +37,10 @@
 
 
 int main(int, char**) {
+#if __cplusplus >= 201703L
+    // Make sure that std::optional can be used with a block, which is the
+    // underlying motivation for making blocks satisfy std::is_scalar.
     std::optional<Foo (^)(Arg<0>)> opt; (void)opt;
+#endif // C++17
     return 0;
 }