diff --git a/src/ox/std/concepts.hpp b/src/ox/std/concepts.hpp
index 1cf0138b1..857e3c40c 100644
--- a/src/ox/std/concepts.hpp
+++ b/src/ox/std/concepts.hpp
@@ -32,4 +32,8 @@ concept Integral_c = ox::is_integral_v<T>;
 
 template<typename T, size_t max>
 concept IntegerRange_c = ox::is_integer_v<T> && ox::MaxValue<T> >= max;
+
+template<typename Union>
+concept Union_c = is_union_v<Union>;
+
 }