diff --git a/src/docs/responsive-design.mdx b/src/docs/responsive-design.mdx
index 4adb3b9a2..9f2ed29fd 100644
--- a/src/docs/responsive-design.mdx
+++ b/src/docs/responsive-design.mdx
@@ -375,6 +375,8 @@ If you need to use a one-off breakpoint that doesn’t make sense to include in
 
 Learn more about arbitrary value support in the [arbitrary values](/docs/adding-custom-styles#using-arbitrary-values) documentation.
 
+Note that CSS variables aren't supported as arbitrary breakpoint values because CSS `@media` queries don't support the `var()` function.
+
 ## Container queries
 
 ### What are container queries?