diff --git a/include/stx/optional.hpp b/include/stx/optional.hpp
index 56be3ce..69ef28b 100644
--- a/include/stx/optional.hpp
+++ b/include/stx/optional.hpp
@@ -37,8 +37,11 @@
             using std::nullopt_t;
             using std::nullopt;
             using std::make_optional;
+#           ifndef STX_HAVE_IN_PLACE_T
             using std::in_place_t;
             using std::in_place;
+#           define STX_HAVE_IN_PLACE_T 1
+#           endif
         }
 #       define STX_HAVE_STD_OPTIONAL 1
 #   elif __has_include(<experimental/optional>)
@@ -49,8 +52,11 @@
             using std::experimental::nullopt_t;
             using std::experimental::nullopt;
             using std::experimental::make_optional;
+#           ifndef STX_HAVE_IN_PLACE_T
             using std::experimental::in_place_t;
             using std::experimental::in_place;
+#           define STX_HAVE_IN_PLACE_T 1
+#           endif
         }
 #       define STX_HAVE_STD_OPTIONAL 1
 #    endif // __hasinclude(optional)
diff --git a/include/stx/variant.hpp b/include/stx/variant.hpp
index dbf79e6..4d6d41c 100644
--- a/include/stx/variant.hpp
+++ b/include/stx/variant.hpp
@@ -57,7 +57,7 @@
 #           ifndef STX_HAVE_IN_PLACE_T
             using std::in_place_t;
             using std::in_place;
-#           define STX_IN_PLACE_T 1
+#           define STX_HAVE_IN_PLACE_T 1
 #           endif
             using std::in_place_type_t;
             using std::in_place_type;