diff --git a/colour/hints/__init__.py b/colour/hints/__init__.py
index 7918cf308..5ad30d7b4 100644
--- a/colour/hints/__init__.py
+++ b/colour/hints/__init__.py
@@ -218,6 +218,9 @@ def apply(self, RGB: ArrayLike, **kwargs: Any) -> NDArray:  # noqa: D102
     "CAM16LCD",
     "CAM16SCD",
     "CAM16UCS",
+    "CIE 1931",
+    "CIE 1960 UCS",
+    "CIE 1976 UCS",
     "CIE Lab",
     "CIE Luv",
     "CIE UCS",